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Science & Nature / Re: Mid September Astronomy Bulletin
« Last post by Clive on September 17, 2018, 22:21 »Now known as the Great Blue Spot. 
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Science & Nature / Re: Mid September Astronomy Bulletin
« Last post by sam on September 17, 2018, 20:42 »Quote
JUPITER HAS AN EXTRA MAGNETIC POLE
Hmmm
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Science & Nature / Mid September Astronomy Bulletin
« Last post by Clive on September 16, 2018, 15:38 »JUPITER HAS AN EXTRA MAGNETIC POLE
Spaceweather.com
When NASA's Juno spacecraft reached Jupiter in 2016, planetary scientists
were eager to learn more about the giant planet's magnetic field. Juno would
fly over both of Jupiter's poles, skimming just 4000 km above the cloud tops
for measurements at point-blank range. Now a team of researchers has
announced that Jupiter's magnetic field is different from all other known
planetary magnetic fields. The best way to appreciate its strangeness is by
comparison with the Earth's. Our planet has two well-defined magnetic poles
-- one in each hemisphere. This is normal. Jupiter's southern hemisphere
looks normal, too. It has a single magnetic pole located near the planet's
spin axis. Jupiter's northern hemisphere, however, is different. The north
magnetic pole is smeared into a swirl, which some writers have likened to a
'ponytail'. And there is a second south pole located near the equator. The
researchers have dubbed that extra pole 'The Great Blue Spot' because it
appears blue in their false-colour images of magnetic polarity. The
scientists consider the possibility that we are catching Jupiter in the
middle of a magnetic reversal -- an unsettled situation with temporary poles
popping up in strange places. However, they favour the idea that Jupiter's
inner magnetic dynamo is simply unlike that of other planets. Deep within
Jupiter, they posit, liquid metallic hydrogen mixes with partially dissolved
rock and ice to create strange electrical currents, giving rise to an
equally strange magnetic field. More clues could be in the offing, as Juno
continues to orbit Jupiter until 2021. Changes to Jupiter's magnetic
structure, for instance, might reveal that a reversal is under way or,
conversely, that the extra pole is stable.
WATER FOUND ON JUPITER
NASA/Goddard Space Flight Center
For centuries, scientists have worked to understand the makeup of Jupiter.
It's no wonder: that planet is the biggest one in the Solar System by far,
and chemically, the closest relative to the Sun. Understanding Jupiter is a
key to learning more about how the Solar System formed, and even about how
other solar systems develop. But one critical question has bedevilled
astronomers for generations: Is there water deep in Jupiter's atmosphere,
and if so, how much? By looking with ground-based telescopes at wavelengths
sensitive to thermal radiation leaking from the depths of Jupiter's
persistent storm, the Great Red Spot, they detected the chemical signatures
of water above the planet's deepest clouds. The pressure of the water, the
researchers concluded, combined with their measurements of another oxygen-
bearing gas, carbon monoxide, imply that Jupiter has 2 to 9 times more
oxygen than the Sun. This finding supports theoretical and computer-
simulation models that have predicted abundant water (H2O) on Jupiter made
of oxygen (O) tied up with molecular hydrogen (H2). The revelation was
stirring, given that the team's experiment could easily have failed. The
Great Red Spot is full of dense clouds, which makes it hard for electromag-
netic energy to escape and teach astronomers anything about the chemistry
within. New spectroscopic technology and sheer curiosity gave the team a
boost in peering deep inside Jupiter, which has an atmosphere thousands of
miles deep. The data the team collected will supplement the information the
Juno spacecraft is gathering as it circles the planet from pole to pole once
every 53 days. Among other things, Juno is looking for water with its own
infrared spectrometer and with a microwave radiometer that can probe deeper
than anyone has seen -- to 100 bars, or 100 times the atmospheric pressure
at Earth's surface. (Altitude on Jupiter is measured in bars, which
represent atmospheric pressure, since the planet has not got a surface,
like the Earth, from which to measure elevation.) If Juno returns similar
water findings, thereby backing the ground-based technique, it could open a
new window into solving the water problem.
Juno is the latest spacecraft tasked with finding water, probably in gas
form, on this giant gaseous planet. Water is a significant and abundant
molecule in our Solar System. It spawned life on Earth and now lubricates
many of its most essential processes, including weather. It is a critical
factor in Jupiter's turbulent weather, too, and in determining whether the
planet has a core made of rock and ice. Jupiter is thought to be the first
planet to have formed by siphoning the elements left over from the formation
of the Sun as our star coalesced from an amorphous nebula into the fiery
ball of gases we see today. A widely accepted theory until several decades
ago was that Jupiter was identical in composition to the Sun -- a ball of
hydrogen with a hint of helium -- all gas, no core. But evidence is mount-
ing that Jupiter has a core, possibly 10 times the Earth's mass. Spacecraft
that previously visited the planet found chemical evidence that it formed a
core of rock and water ice before it mixed with gases from the solar nebula
to make its atmosphere. The way Jupiter's gravity acts on Juno also
supports that theory. There's even lightning and thunder on the planet,
phenomena fuelled by moisture. The moons that orbit Jupiter are mostly
water ice, so the whole neighbourhood has plenty of water. Why wouldn't the
planet -- which is this huge gravity well, where everything falls into it --
be water rich, too? In its search for water, the team used radiation data
collected from the summit of Mauna Kea in Hawaii in 2017. They relied on
the most sensitive infrared telescope on Earth at the W.M. Keck Observatory,
and also on a new instrument that can detect a wider range of gases at the
NASA Infrared Telescope Facility. The idea was to analyze the light energy
emitted through Jupiter's clouds in order to identify the altitudes of its
cloud layers. That would help the scientists determine temperature and
other conditions that influence the types of gases that can survive in those
regions. Planetary-atmosphere experts expect that there are three cloud
layers on Jupiter: a lower layer made of water ice and liquid water, a
middle one made of ammonia and sulphur, and an upper layer made of ammonia.
To check that through ground-based observations, the team looked at wave-
lengths in the infrared range of light where most gases don't absorb heat,
allowing chemical signatures to leak out. Specifically, they analyzed the
absorption patterns of a form of methane gas. Because Jupiter is too warm
for methane to freeze, its abundance should not change from one place to
another on the planet. The team found evidence for the three cloud layers
in the Great Red Spot, supporting earlier models. The deepest cloud layer
is at 5 bars, the team concluded, right where the temperature reaches the
freezing point of water. The location of the water cloud, plus the amount
of carbon monoxide that the researchers identified on Jupiter, confirms that
Jupiter is rich in oxygen and, thus, water. The technique now needs to be
tested on other parts of Jupiter to get a full picture of global water
abundance, and the data squared with Juno's findings.
PLUTO SHOULD BE RECLASSIFIED AS A PLANET
University of Central Florida
In 2006, the International Astronomical Union established a definition of a
planet that required it to "clear" its orbit, or in other words, be the
largest gravitational force in its orbit. Since Neptune's gravity influences
its neighbouring planet Pluto, and Pluto shares its orbit with frozen gases
and objects in the Kuiper belt, that meant Pluto was out of planet status.
However, a new study reports that that standard for classifying planets is
not supported in the research literature. The study reviewed scientific
literature from the past 200 years and found only one publication -- from
1802 -- that used the clearing-orbit requirement to classify planets, and it
was based on since-disproved reasoning. Moons such as Saturn's Titan and
Jupiter's Europa have been routinely called planets by planetary scientists
since the time of Galileo. The IAU definition would mean that the funda-
mental object of planetary science, the planet, is supposed to be a defined
on the basis of a concept that nobody uses in their research. It would
leave out the second-most-complex, interesting planet in the Solar System.
We now have a list of well over 100 recent examples of planetary scientists
using the word planet in a way that violates the IAU definition, but they
are doing it because it is functionally useful. They didn't say what they
meant by clearing their orbit. If you take that literally, then there are
no planets, because no planet clears its orbit.
The study said that the literature review showed that the real division
between planets and other celestial bodies, such as asteroids, occurred in
the early 1950s when Gerard Kuiper published a paper that made the distinc-
tion based on how they were formed. However, even that reason is no longer
considered a factor that determines if a celestial body is a planet.
The IAU's definition is erroneous, since the literature review shows that
clearing of the orbit is not a standard that is used for distinguishing
asteroids from planets, as the IAU claimed when crafting the 2006 definition
of planets. Instead, the study recommends classifying a planet on the basis
of whether it is large enough for its gravity causes it to become spherical
in shape. Pluto, for instance, has an underground ocean, a multi-layer
atmosphere, organic compounds, evidence of ancient lakes and multiple moons,
he said. It is more dynamic than Mars. The only planet that has more
complex geology is the Earth.
EXPOLANET FOUND VERY CLOSE TO STAR
Universite de Montreal
Wolf 503b, an exoplanet twice the size of the Earth, has been discovered
by an international team of researchers using data from the Kepler Space
Telescope. Wolf 503b is about 145 light-years from the Earth in the Virgo
constellation; it orbits its star every six days and is thus very close to
it, about 10 times closer than Mercury is to the Sun. The team identified
distinct, periodic dips such as appear in the light-curve of a star when a
planet passes in front of it. In order to characterize better the system of
which Wolf 503b is part, the astronomers first obtained a spectrum of the
host star at the NASA Infrared Telescope Facility. That confirmed that the
star is an old 'orange dwarf', slightly less luminous than the Sun but about
twice as old, and allowed precise determinations of the radii both of the
star and its companion. To confirm that the companion was indeed a planet
and to avoid making a false positive identification, the team obtained
adaptive-optics measurements from Palomar Observatory and also examined
archival data. With those, they were able to confirm that there were no
binary stars in the background and that the star did not have another, more
massive, companion that could be interpreted as a transiting planet. Wolf
503b is interesting, first, because of its size. Thanks to the Kepler
telescope, we know that most of the planets in the Milky Way that orbit
close to their stars are about as big as Wolf 503b, somewhere between the
the sizes of the Earth and Neptune (which is four times bigger than the
Earth). Since there is nothing like them in the Solar System, astronomers
wonder whether these planets are small and rocky 'super-Earths' or gaseous
mini versions of Neptune. One recent discovery also shows that there are
significantly fewer planets that are between 1.5 and 2 times the size of the
Earth than those either smaller or larger than that. In their study of the
discovery, published in 2017, the researchers say that that gap, called the
Fulton gap, could be what distinguishes the two types of planets from one
another.
Wolf 503b is one of the only planets with a radius near the gap that has a
star that is bright enough to be accessible to more detailed study that will
constrain its true nature better. The second reason for interest in the
Wolf 503b system is that the star is relatively close to the Earth, and is
bright. One of the possible follow-up studies for bright stars is the
measurement of their radial velocities to determine the masses of the
planets in orbit around them. A more massive planet will have a greater
gravitational influence on its star, and the variation in line-of-sight
velocity of the star over time will be greater. The mass, together with the
radius determined by Kepler's observations, gives the bulk density of the
planet, which in turn may tell us something about its composition. For
example, at its radius, if the planet has a composition similar to that of
the Earth, it would have to be about 14 times ithe Earth's mass. If, like
Neptune, it has an atmosphere rich in gas or volatiles, it would be
approximately half as massive. Because of its brightness, Wolf 503 will
also be a prime target for the upcoming James Webb Space Telescope.
Using a technique called transit spectroscopy, it will be possible to study the
chemical content of the planet's atmosphere, and to detect the presence of
molecules like hydrogen and water. That is crucial to determine whether its
atmosphere is similar to that of the Earth, or that of Neptune, or entirely
different from the atmospheres of planets in the Solar System. Similar
observations can not be made of most planets found by Kepler, because their
host stars are usually much fainter. As a result, the bulk densities and
atmospheric compositions of most exoplanets are still unknown.
LITTLE STAR SHEDS LIGHT ON YOUNG PLANETS
University of Tokyo
The star IRAS 15398-3359) is small, young and relatively cool. Its dimin-
utive stature means that the weak light that it shines with can't even reach
us through a cloud of gas and dust that surrounds it. But that does not
stop inquisitive minds from exploring the unknown. In 2013, astronomers
used the Atacama Large Millimetre/sub-millimetre Array (ALMA) in Chile to
observe the star in sub-millimetre wavelengths, as that kind of light can
penetrate the dust cloud. Analysis revealed some interesting nebulous
structures, despite the images the astronomers worked from being difficult
to comprehend. The model describes a dense disc of material that consists
of gas and dust from the cloud that surrounds the star. Such a disc has not
previously been seen around such a young star. The disc is a precursor to a
protoplanetary disc, which is far denser still and eventually becomes a
planetary system in orbit around a star. Astronomers can't say for sure
that this particular disc will coalesce into a new planetary system. The
dust cloud may be pushed away by stellar winds or it might all fall into the
star itself. What is exciting is how quickly that might happen. The star
is small, at around 0.7 per cent of the mass of the Sun, on the basis of
observations of the mass of the surrounding cloud. It could grow to as
large as 20 per cent in just a few tens of thousands of years, a blink of
the eye on the cosmic scale. The observations and resultant model were only
possible thanks to advances in radio astronomy with observatories such as
ALMA. The team was lucky that we see the disc practically edge-on, so the
starlight ALMA sees passes through enough of the gas and dust of the disc to
divulge important characteristics of it.
SUPERNOVAE CLUE TO STELLAR EVOLUTION
National Institutes of Natural Sciences
At the end of its life, a red supergiant star explodes as a hydrogen-rich
supernova. By comparing observational results to simulation models, an
international research team found that in many cases the explosion takes
place inside a thick cloud of circumstellar matter shrouding the star. That
result completely changes our understanding of the last stage of stellar
evolution. The research team used the Blanco Telescope to find 26 super-
novae coming from red supergiants. Their goal was to study the shock
breakout, a brief flash of light preceding the main supernova explosion.
But they could not find any signs of that phenomenon. On the other hand, 24
of the supernovae brightened faster than expected. To solve that mystery,
astronomers simulated 518 models of supernova brightness variations and
compared them with the observational results. The team found that models
with a layer of circumstellar matter about 10% of the mass of the Sun
surrounding the supernovae matched the observations well. The circumstellar
matter hides the shock breakout, trapping its light. The subsequent
collision between the supernova ejecta and the circumstellar matter creates
a strong shock wave that produces extra light, causing it to brighten more
quickly. Near the end of its life, some mechanism in the star's interior
must cause it to shed mass that then forms a layer around the star. We do
not yet have a clear idea of the mechanism causing such mass loss; further
study is needed. That will also be important in revealing the supernova
explosion mechanism and the origin of the diversity in supernovae.
CONFIRMATION OF SUPER-FAST JET FROM STAR MERGER
National Radio Astronomy Observatory
Precise measurement using a continent-wide collection of National Science
Foundation (NSF) radio telescopes has revealed that a narrow jet of
particles moving at nearly the speed of light broke out into interstellar
space after a pair of neutron stars merged in a galaxy 130 million light-
years away. The merger, which occurred in 2017 August, sent gravitational
waves rippling through space. It was the first event ever to be detected
both by gravitational waves and electromagnetic waves, including gamma rays,
X-rays, visible light, and radio waves. The aftermath of the merger, called
GW170817, was observed by orbiting and ground-based telescopes around the
world. Scientists watched as the characteristics of the received waves
changed with time, and used the changes as clues to reveal the nature of the
phenomena that followed the merger. One question that stood out, even
months after the merger, was whether or not the event had produced a narrow,
fast-moving jet of material that made its way into interstellar space. That
was important, because such jets are required to produce the type of gamma-
ray bursts that theorists had said should be caused by the merger of
neutron-star pairs. The answer came when astronomers used a combination of
the NSF's Very Long Baseline Array (VLBA), the Karl G. Jansky Very Large
Array (VLA), and the Robert C. Byrd Green Bank Telescope (GBT) and discovered
that a region of radio emission from the merger had moved, and the motion was
so fast that only a jet could explain its speed. They measured an
apparent motion that is four times faster than light. That illusion, called
superluminal motion, results when the jet is pointed nearly towards the
Earth and the material in the jet is moving close to the speed of light.
The astronomers observed the object 75 days after the merger, then again 230
days after. The jet is likely to be very narrow, at most 5 degrees wide,
and was pointed only 20 degrees away from the Earth's direction. To match
the observations, the material in the jet has to be blasting outwards at
over 97% of the speed of light.
The scenario that emerges is that the initial merger of the two super-dense
neutron stars caused an explosion that propelled a spherical shell of debris
outward. The neutron stars collapsed into a black hole whose powerful
gravity began pulling material towards it. That material formed a rapidly-
spinning disc that generated a pair of jets moving outwards from its poles.
As the event unfolded, the question became whether the jets would break out
of the shell of debris from the original explosion. Data from observations
indicated that a jet had interacted with the debris, forming a broad
'cocoon' of material expanding outward. Such a cocoon would expand more
slowly than a jet. The scientists said that the detection of a fast-moving
jet in GW170817 greatly strengthens the connection between neutron-star
mergers and short-duration gamma-ray bursts. They added that the jets need
to be pointed relatively accurately towards the Earth for the gamma-ray
burst to be detected. The merger event was important for a number of
reasons, and it continues to surprise astronomers with more information.
Jets are enigmatic phenomena seen in a number of environments, and now
these exquisite observations in the radio part of the electromagnetic spectrum
are providing fascinating insight into them, helping us to understand how they
work.
UNSTOPPABLE MONSTER IN EARLY UNIVERSE:
National Institutes of Natural Sciences
Astronomers have obtained the most detailed anatomy chart of a monster
galaxy located 12.4 billion light-years away. Using the Atacama Large
Millimetre/submillimetre Array (ALMA), the team revealed that the molecular
clouds in the galaxy are highly unstable, which leads to runaway star
formation. Monster galaxies are thought to be the ancestors of the huge
elliptical galaxies in today's Universe, therefore these findings pave the
way to understand the formation and evolution of such galaxies. Monster
galaxies, or starburst galaxies, form stars at a startling pace, 1000 times
higher than the star formation in our Galaxy. But why are they so active?
To tackle that problem, researchers need to know the environment around the
stellar nurseries. Drawing detailed maps of molecular clouds is an important
step to scout a cosmic monster. The team targeted a chimerical galaxy,
COSMOS-AzTEC-1. That galaxy was first discovered with the James Clerk
Maxwell Telescope in Hawaii, and later the Large Millimetre Telescope (LMT)
in Mexico found an enormous amount of carbon monoxide gas in the galaxy and
revealed its hidden starburst. The LMT observations also measured the
distance to the galaxy, and found that it is 12.4 US-billion light-years.
Researchers have found that COSMOS-AzTEC-1 is rich with the ingredients of
stars, but it was still difficult to figure out the nature of the cosmic gas
in the galaxy. The team utilized the high resolution and high sensitivity
of ALMA to observe this monster galaxy and obtain a detailed map of the
distribution and the motion of the gas. Thanks to the most extended ALMA
antenna configuration of 16 km, this is the highest-resolution molecular-gas
map of a distant monster galaxy ever made.
The team found that there are two distinct large clouds several thousand
light-years away from the centre. In most distant starburst galaxies, stars
are actively formed in the centre, so it is surprising to find off-centre
clouds. The astronomers further investigated the nature of the gas in
COSMOS-AzTEC-1 and found that the clouds throughout the galaxy are very
unstable, which is unusual. In a normal situation, the inward gravity and
outward pressure are balanced in the clouds. Once gravity overcomes
pressure, the gas cloud collapses and forms stars at a rapid pace. Then,
stars and supernova explosions at the end of the stellar life-cycle blast
out gases, which increase the outward pressure. As a result, the gravity
and pressure reach a balanced state and star formation continues at a
moderate pace. In that way star formation in galaxies is self-regulating.
But, in COSMOS-AzTEC-1, the pressure is far weaker than the gravity and hard
to balance. Therefore that galaxy shows runaway star formation and has
morphed into an unstoppable monster galaxy. The team estimated that the gas
in COSMOS-AzTEC-1 will be completely consumed in 100 million years, which is
10 times faster than in other star-forming galaxies. But why is the gas in
COSMOS-AzTEC-1 so unstable? Researchers have not got a definitive answer
yet, but galaxy merger is a possible cause. Galaxy collision may have
transported the gas efficiently into a small area and ignited intense star
formation. At this moment, however, astronomers have no evidence of any
merger in that galaxy. By observing other similar galaxies with ALMA,
astronomers hope to elucidate the relationship between galaxy mergers and
monster galaxies.
Spaceweather.com
When NASA's Juno spacecraft reached Jupiter in 2016, planetary scientists
were eager to learn more about the giant planet's magnetic field. Juno would
fly over both of Jupiter's poles, skimming just 4000 km above the cloud tops
for measurements at point-blank range. Now a team of researchers has
announced that Jupiter's magnetic field is different from all other known
planetary magnetic fields. The best way to appreciate its strangeness is by
comparison with the Earth's. Our planet has two well-defined magnetic poles
-- one in each hemisphere. This is normal. Jupiter's southern hemisphere
looks normal, too. It has a single magnetic pole located near the planet's
spin axis. Jupiter's northern hemisphere, however, is different. The north
magnetic pole is smeared into a swirl, which some writers have likened to a
'ponytail'. And there is a second south pole located near the equator. The
researchers have dubbed that extra pole 'The Great Blue Spot' because it
appears blue in their false-colour images of magnetic polarity. The
scientists consider the possibility that we are catching Jupiter in the
middle of a magnetic reversal -- an unsettled situation with temporary poles
popping up in strange places. However, they favour the idea that Jupiter's
inner magnetic dynamo is simply unlike that of other planets. Deep within
Jupiter, they posit, liquid metallic hydrogen mixes with partially dissolved
rock and ice to create strange electrical currents, giving rise to an
equally strange magnetic field. More clues could be in the offing, as Juno
continues to orbit Jupiter until 2021. Changes to Jupiter's magnetic
structure, for instance, might reveal that a reversal is under way or,
conversely, that the extra pole is stable.
WATER FOUND ON JUPITER
NASA/Goddard Space Flight Center
For centuries, scientists have worked to understand the makeup of Jupiter.
It's no wonder: that planet is the biggest one in the Solar System by far,
and chemically, the closest relative to the Sun. Understanding Jupiter is a
key to learning more about how the Solar System formed, and even about how
other solar systems develop. But one critical question has bedevilled
astronomers for generations: Is there water deep in Jupiter's atmosphere,
and if so, how much? By looking with ground-based telescopes at wavelengths
sensitive to thermal radiation leaking from the depths of Jupiter's
persistent storm, the Great Red Spot, they detected the chemical signatures
of water above the planet's deepest clouds. The pressure of the water, the
researchers concluded, combined with their measurements of another oxygen-
bearing gas, carbon monoxide, imply that Jupiter has 2 to 9 times more
oxygen than the Sun. This finding supports theoretical and computer-
simulation models that have predicted abundant water (H2O) on Jupiter made
of oxygen (O) tied up with molecular hydrogen (H2). The revelation was
stirring, given that the team's experiment could easily have failed. The
Great Red Spot is full of dense clouds, which makes it hard for electromag-
netic energy to escape and teach astronomers anything about the chemistry
within. New spectroscopic technology and sheer curiosity gave the team a
boost in peering deep inside Jupiter, which has an atmosphere thousands of
miles deep. The data the team collected will supplement the information the
Juno spacecraft is gathering as it circles the planet from pole to pole once
every 53 days. Among other things, Juno is looking for water with its own
infrared spectrometer and with a microwave radiometer that can probe deeper
than anyone has seen -- to 100 bars, or 100 times the atmospheric pressure
at Earth's surface. (Altitude on Jupiter is measured in bars, which
represent atmospheric pressure, since the planet has not got a surface,
like the Earth, from which to measure elevation.) If Juno returns similar
water findings, thereby backing the ground-based technique, it could open a
new window into solving the water problem.
Juno is the latest spacecraft tasked with finding water, probably in gas
form, on this giant gaseous planet. Water is a significant and abundant
molecule in our Solar System. It spawned life on Earth and now lubricates
many of its most essential processes, including weather. It is a critical
factor in Jupiter's turbulent weather, too, and in determining whether the
planet has a core made of rock and ice. Jupiter is thought to be the first
planet to have formed by siphoning the elements left over from the formation
of the Sun as our star coalesced from an amorphous nebula into the fiery
ball of gases we see today. A widely accepted theory until several decades
ago was that Jupiter was identical in composition to the Sun -- a ball of
hydrogen with a hint of helium -- all gas, no core. But evidence is mount-
ing that Jupiter has a core, possibly 10 times the Earth's mass. Spacecraft
that previously visited the planet found chemical evidence that it formed a
core of rock and water ice before it mixed with gases from the solar nebula
to make its atmosphere. The way Jupiter's gravity acts on Juno also
supports that theory. There's even lightning and thunder on the planet,
phenomena fuelled by moisture. The moons that orbit Jupiter are mostly
water ice, so the whole neighbourhood has plenty of water. Why wouldn't the
planet -- which is this huge gravity well, where everything falls into it --
be water rich, too? In its search for water, the team used radiation data
collected from the summit of Mauna Kea in Hawaii in 2017. They relied on
the most sensitive infrared telescope on Earth at the W.M. Keck Observatory,
and also on a new instrument that can detect a wider range of gases at the
NASA Infrared Telescope Facility. The idea was to analyze the light energy
emitted through Jupiter's clouds in order to identify the altitudes of its
cloud layers. That would help the scientists determine temperature and
other conditions that influence the types of gases that can survive in those
regions. Planetary-atmosphere experts expect that there are three cloud
layers on Jupiter: a lower layer made of water ice and liquid water, a
middle one made of ammonia and sulphur, and an upper layer made of ammonia.
To check that through ground-based observations, the team looked at wave-
lengths in the infrared range of light where most gases don't absorb heat,
allowing chemical signatures to leak out. Specifically, they analyzed the
absorption patterns of a form of methane gas. Because Jupiter is too warm
for methane to freeze, its abundance should not change from one place to
another on the planet. The team found evidence for the three cloud layers
in the Great Red Spot, supporting earlier models. The deepest cloud layer
is at 5 bars, the team concluded, right where the temperature reaches the
freezing point of water. The location of the water cloud, plus the amount
of carbon monoxide that the researchers identified on Jupiter, confirms that
Jupiter is rich in oxygen and, thus, water. The technique now needs to be
tested on other parts of Jupiter to get a full picture of global water
abundance, and the data squared with Juno's findings.
PLUTO SHOULD BE RECLASSIFIED AS A PLANET
University of Central Florida
In 2006, the International Astronomical Union established a definition of a
planet that required it to "clear" its orbit, or in other words, be the
largest gravitational force in its orbit. Since Neptune's gravity influences
its neighbouring planet Pluto, and Pluto shares its orbit with frozen gases
and objects in the Kuiper belt, that meant Pluto was out of planet status.
However, a new study reports that that standard for classifying planets is
not supported in the research literature. The study reviewed scientific
literature from the past 200 years and found only one publication -- from
1802 -- that used the clearing-orbit requirement to classify planets, and it
was based on since-disproved reasoning. Moons such as Saturn's Titan and
Jupiter's Europa have been routinely called planets by planetary scientists
since the time of Galileo. The IAU definition would mean that the funda-
mental object of planetary science, the planet, is supposed to be a defined
on the basis of a concept that nobody uses in their research. It would
leave out the second-most-complex, interesting planet in the Solar System.
We now have a list of well over 100 recent examples of planetary scientists
using the word planet in a way that violates the IAU definition, but they
are doing it because it is functionally useful. They didn't say what they
meant by clearing their orbit. If you take that literally, then there are
no planets, because no planet clears its orbit.
The study said that the literature review showed that the real division
between planets and other celestial bodies, such as asteroids, occurred in
the early 1950s when Gerard Kuiper published a paper that made the distinc-
tion based on how they were formed. However, even that reason is no longer
considered a factor that determines if a celestial body is a planet.
The IAU's definition is erroneous, since the literature review shows that
clearing of the orbit is not a standard that is used for distinguishing
asteroids from planets, as the IAU claimed when crafting the 2006 definition
of planets. Instead, the study recommends classifying a planet on the basis
of whether it is large enough for its gravity causes it to become spherical
in shape. Pluto, for instance, has an underground ocean, a multi-layer
atmosphere, organic compounds, evidence of ancient lakes and multiple moons,
he said. It is more dynamic than Mars. The only planet that has more
complex geology is the Earth.
EXPOLANET FOUND VERY CLOSE TO STAR
Universite de Montreal
Wolf 503b, an exoplanet twice the size of the Earth, has been discovered
by an international team of researchers using data from the Kepler Space
Telescope. Wolf 503b is about 145 light-years from the Earth in the Virgo
constellation; it orbits its star every six days and is thus very close to
it, about 10 times closer than Mercury is to the Sun. The team identified
distinct, periodic dips such as appear in the light-curve of a star when a
planet passes in front of it. In order to characterize better the system of
which Wolf 503b is part, the astronomers first obtained a spectrum of the
host star at the NASA Infrared Telescope Facility. That confirmed that the
star is an old 'orange dwarf', slightly less luminous than the Sun but about
twice as old, and allowed precise determinations of the radii both of the
star and its companion. To confirm that the companion was indeed a planet
and to avoid making a false positive identification, the team obtained
adaptive-optics measurements from Palomar Observatory and also examined
archival data. With those, they were able to confirm that there were no
binary stars in the background and that the star did not have another, more
massive, companion that could be interpreted as a transiting planet. Wolf
503b is interesting, first, because of its size. Thanks to the Kepler
telescope, we know that most of the planets in the Milky Way that orbit
close to their stars are about as big as Wolf 503b, somewhere between the
the sizes of the Earth and Neptune (which is four times bigger than the
Earth). Since there is nothing like them in the Solar System, astronomers
wonder whether these planets are small and rocky 'super-Earths' or gaseous
mini versions of Neptune. One recent discovery also shows that there are
significantly fewer planets that are between 1.5 and 2 times the size of the
Earth than those either smaller or larger than that. In their study of the
discovery, published in 2017, the researchers say that that gap, called the
Fulton gap, could be what distinguishes the two types of planets from one
another.
Wolf 503b is one of the only planets with a radius near the gap that has a
star that is bright enough to be accessible to more detailed study that will
constrain its true nature better. The second reason for interest in the
Wolf 503b system is that the star is relatively close to the Earth, and is
bright. One of the possible follow-up studies for bright stars is the
measurement of their radial velocities to determine the masses of the
planets in orbit around them. A more massive planet will have a greater
gravitational influence on its star, and the variation in line-of-sight
velocity of the star over time will be greater. The mass, together with the
radius determined by Kepler's observations, gives the bulk density of the
planet, which in turn may tell us something about its composition. For
example, at its radius, if the planet has a composition similar to that of
the Earth, it would have to be about 14 times ithe Earth's mass. If, like
Neptune, it has an atmosphere rich in gas or volatiles, it would be
approximately half as massive. Because of its brightness, Wolf 503 will
also be a prime target for the upcoming James Webb Space Telescope.
Using a technique called transit spectroscopy, it will be possible to study the
chemical content of the planet's atmosphere, and to detect the presence of
molecules like hydrogen and water. That is crucial to determine whether its
atmosphere is similar to that of the Earth, or that of Neptune, or entirely
different from the atmospheres of planets in the Solar System. Similar
observations can not be made of most planets found by Kepler, because their
host stars are usually much fainter. As a result, the bulk densities and
atmospheric compositions of most exoplanets are still unknown.
LITTLE STAR SHEDS LIGHT ON YOUNG PLANETS
University of Tokyo
The star IRAS 15398-3359) is small, young and relatively cool. Its dimin-
utive stature means that the weak light that it shines with can't even reach
us through a cloud of gas and dust that surrounds it. But that does not
stop inquisitive minds from exploring the unknown. In 2013, astronomers
used the Atacama Large Millimetre/sub-millimetre Array (ALMA) in Chile to
observe the star in sub-millimetre wavelengths, as that kind of light can
penetrate the dust cloud. Analysis revealed some interesting nebulous
structures, despite the images the astronomers worked from being difficult
to comprehend. The model describes a dense disc of material that consists
of gas and dust from the cloud that surrounds the star. Such a disc has not
previously been seen around such a young star. The disc is a precursor to a
protoplanetary disc, which is far denser still and eventually becomes a
planetary system in orbit around a star. Astronomers can't say for sure
that this particular disc will coalesce into a new planetary system. The
dust cloud may be pushed away by stellar winds or it might all fall into the
star itself. What is exciting is how quickly that might happen. The star
is small, at around 0.7 per cent of the mass of the Sun, on the basis of
observations of the mass of the surrounding cloud. It could grow to as
large as 20 per cent in just a few tens of thousands of years, a blink of
the eye on the cosmic scale. The observations and resultant model were only
possible thanks to advances in radio astronomy with observatories such as
ALMA. The team was lucky that we see the disc practically edge-on, so the
starlight ALMA sees passes through enough of the gas and dust of the disc to
divulge important characteristics of it.
SUPERNOVAE CLUE TO STELLAR EVOLUTION
National Institutes of Natural Sciences
At the end of its life, a red supergiant star explodes as a hydrogen-rich
supernova. By comparing observational results to simulation models, an
international research team found that in many cases the explosion takes
place inside a thick cloud of circumstellar matter shrouding the star. That
result completely changes our understanding of the last stage of stellar
evolution. The research team used the Blanco Telescope to find 26 super-
novae coming from red supergiants. Their goal was to study the shock
breakout, a brief flash of light preceding the main supernova explosion.
But they could not find any signs of that phenomenon. On the other hand, 24
of the supernovae brightened faster than expected. To solve that mystery,
astronomers simulated 518 models of supernova brightness variations and
compared them with the observational results. The team found that models
with a layer of circumstellar matter about 10% of the mass of the Sun
surrounding the supernovae matched the observations well. The circumstellar
matter hides the shock breakout, trapping its light. The subsequent
collision between the supernova ejecta and the circumstellar matter creates
a strong shock wave that produces extra light, causing it to brighten more
quickly. Near the end of its life, some mechanism in the star's interior
must cause it to shed mass that then forms a layer around the star. We do
not yet have a clear idea of the mechanism causing such mass loss; further
study is needed. That will also be important in revealing the supernova
explosion mechanism and the origin of the diversity in supernovae.
CONFIRMATION OF SUPER-FAST JET FROM STAR MERGER
National Radio Astronomy Observatory
Precise measurement using a continent-wide collection of National Science
Foundation (NSF) radio telescopes has revealed that a narrow jet of
particles moving at nearly the speed of light broke out into interstellar
space after a pair of neutron stars merged in a galaxy 130 million light-
years away. The merger, which occurred in 2017 August, sent gravitational
waves rippling through space. It was the first event ever to be detected
both by gravitational waves and electromagnetic waves, including gamma rays,
X-rays, visible light, and radio waves. The aftermath of the merger, called
GW170817, was observed by orbiting and ground-based telescopes around the
world. Scientists watched as the characteristics of the received waves
changed with time, and used the changes as clues to reveal the nature of the
phenomena that followed the merger. One question that stood out, even
months after the merger, was whether or not the event had produced a narrow,
fast-moving jet of material that made its way into interstellar space. That
was important, because such jets are required to produce the type of gamma-
ray bursts that theorists had said should be caused by the merger of
neutron-star pairs. The answer came when astronomers used a combination of
the NSF's Very Long Baseline Array (VLBA), the Karl G. Jansky Very Large
Array (VLA), and the Robert C. Byrd Green Bank Telescope (GBT) and discovered
that a region of radio emission from the merger had moved, and the motion was
so fast that only a jet could explain its speed. They measured an
apparent motion that is four times faster than light. That illusion, called
superluminal motion, results when the jet is pointed nearly towards the
Earth and the material in the jet is moving close to the speed of light.
The astronomers observed the object 75 days after the merger, then again 230
days after. The jet is likely to be very narrow, at most 5 degrees wide,
and was pointed only 20 degrees away from the Earth's direction. To match
the observations, the material in the jet has to be blasting outwards at
over 97% of the speed of light.
The scenario that emerges is that the initial merger of the two super-dense
neutron stars caused an explosion that propelled a spherical shell of debris
outward. The neutron stars collapsed into a black hole whose powerful
gravity began pulling material towards it. That material formed a rapidly-
spinning disc that generated a pair of jets moving outwards from its poles.
As the event unfolded, the question became whether the jets would break out
of the shell of debris from the original explosion. Data from observations
indicated that a jet had interacted with the debris, forming a broad
'cocoon' of material expanding outward. Such a cocoon would expand more
slowly than a jet. The scientists said that the detection of a fast-moving
jet in GW170817 greatly strengthens the connection between neutron-star
mergers and short-duration gamma-ray bursts. They added that the jets need
to be pointed relatively accurately towards the Earth for the gamma-ray
burst to be detected. The merger event was important for a number of
reasons, and it continues to surprise astronomers with more information.
Jets are enigmatic phenomena seen in a number of environments, and now
these exquisite observations in the radio part of the electromagnetic spectrum
are providing fascinating insight into them, helping us to understand how they
work.
UNSTOPPABLE MONSTER IN EARLY UNIVERSE:
National Institutes of Natural Sciences
Astronomers have obtained the most detailed anatomy chart of a monster
galaxy located 12.4 billion light-years away. Using the Atacama Large
Millimetre/submillimetre Array (ALMA), the team revealed that the molecular
clouds in the galaxy are highly unstable, which leads to runaway star
formation. Monster galaxies are thought to be the ancestors of the huge
elliptical galaxies in today's Universe, therefore these findings pave the
way to understand the formation and evolution of such galaxies. Monster
galaxies, or starburst galaxies, form stars at a startling pace, 1000 times
higher than the star formation in our Galaxy. But why are they so active?
To tackle that problem, researchers need to know the environment around the
stellar nurseries. Drawing detailed maps of molecular clouds is an important
step to scout a cosmic monster. The team targeted a chimerical galaxy,
COSMOS-AzTEC-1. That galaxy was first discovered with the James Clerk
Maxwell Telescope in Hawaii, and later the Large Millimetre Telescope (LMT)
in Mexico found an enormous amount of carbon monoxide gas in the galaxy and
revealed its hidden starburst. The LMT observations also measured the
distance to the galaxy, and found that it is 12.4 US-billion light-years.
Researchers have found that COSMOS-AzTEC-1 is rich with the ingredients of
stars, but it was still difficult to figure out the nature of the cosmic gas
in the galaxy. The team utilized the high resolution and high sensitivity
of ALMA to observe this monster galaxy and obtain a detailed map of the
distribution and the motion of the gas. Thanks to the most extended ALMA
antenna configuration of 16 km, this is the highest-resolution molecular-gas
map of a distant monster galaxy ever made.
The team found that there are two distinct large clouds several thousand
light-years away from the centre. In most distant starburst galaxies, stars
are actively formed in the centre, so it is surprising to find off-centre
clouds. The astronomers further investigated the nature of the gas in
COSMOS-AzTEC-1 and found that the clouds throughout the galaxy are very
unstable, which is unusual. In a normal situation, the inward gravity and
outward pressure are balanced in the clouds. Once gravity overcomes
pressure, the gas cloud collapses and forms stars at a rapid pace. Then,
stars and supernova explosions at the end of the stellar life-cycle blast
out gases, which increase the outward pressure. As a result, the gravity
and pressure reach a balanced state and star formation continues at a
moderate pace. In that way star formation in galaxies is self-regulating.
But, in COSMOS-AzTEC-1, the pressure is far weaker than the gravity and hard
to balance. Therefore that galaxy shows runaway star formation and has
morphed into an unstoppable monster galaxy. The team estimated that the gas
in COSMOS-AzTEC-1 will be completely consumed in 100 million years, which is
10 times faster than in other star-forming galaxies. But why is the gas in
COSMOS-AzTEC-1 so unstable? Researchers have not got a definitive answer
yet, but galaxy merger is a possible cause. Galaxy collision may have
transported the gas efficiently into a small area and ignited intense star
formation. At this moment, however, astronomers have no evidence of any
merger in that galaxy. By observing other similar galaxies with ALMA,
astronomers hope to elucidate the relationship between galaxy mergers and
monster galaxies.
4
Science & Nature / Early September Astronomy Bulletin
« Last post by Clive on September 16, 2018, 15:36 »STUDY SHOWS EARTH’S INGREDIENTS ARE NORMAL
Goldschmidt Conference
The Earth's building blocks seem to be built from 'pretty normal' ingredients, according to researchers working with the world's most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth. This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere. The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system. It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves. Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense -- it is anticipated that our Sun will become a white dwarf in around 5 billion years. White dwarfs' atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn. As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star's spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected.
The team took measurements using spectrographs on the Keck telescope in Hawaii, the world's largest optical and infrared telescope, and on the Hubble Space Telescope. In this study, the team focused on the sample of white dwarfs with dust disks. Astronomers were able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. They may also have found water in one of the systems, but have not yet quantified it: it's likely that there will be a lot of water in some of these worlds. For example, the team previously identified one star system, 170 light years away in the constellation Boötes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley's Comet. In general though, their composition looks very similar to bulk Earth. This would mean that the chemical elements, the building blocks of Earth are common in other planetary systems. From what can be seen, in terms of the presence and proportion of these elements, we're normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy. This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. The team hopes to determine the chemical compositions of extrasolar planetary material to a much higher precision.
A GREEN COMET APPROACHES EARTH
Spaceweather.com
Comet 21P/Giacobini-Zinner is approaching Earth. On Sept. 10th, it will be 0.39 AU (58 million km) from our planet and almost bright enough to see with the naked eye. Already it is an easy target for amateur telescopes. This comet is relatively small--its nucleus is barely more than a mile in diameter--but it is bright and active, and a frequent visitor to the inner solar system as it orbits the Sun once every 6.6 years. On Sept. 10th, 21P/Giacobini-Zinner will not only be near Earth, but also at perihelion, its closest approach to the Sun. Solar heating will make it shine like a star of 6th to 7th magnitude, just below the threshold of naked-eye visibility and well within range of common binoculars. 21P/Giacobini-Zinner is the parent of the annual Draconid meteor shower, a bursty display that typically peaks on Oct. 8th. Will the shower will be extra-good this year? Maybe. Draconid outbursts do tend to occur in years near the comet's close approach to the sun. However, not every close approach brings a meteor shower. Forecasters say there are no known Draconid debris streams squarely crossing Earth's path this year, so we will have to wait and see.
ICE CONFIRMED AT MOON’S POLES
NASA/Jet Propulsion Laboratory
In the darkest and coldest parts of its polar regions, a team of scientists has directly observed definitive evidence of water ice on the Moon's surface. These ice deposits are patchily distributed and could possibly be ancient. At the southern pole, most of the ice is concentrated at lunar craters, while the northern pole's ice is more widely, but sparsely spread. A team of scientists used data from NASA's Moon Mineralogy Mapper (M3) instrument to identify three specific signatures that definitively prove there is water ice at the surface of the Moon. M3, aboard the Chandrayaan-1 spacecraft, launched in 2008 by the Indian Space Research Organization, was equipped to confirm the presence of solid ice on the Moon. It collected data that not only picked up the reflective properties we'd expect from ice, but was able to directly measure the distinctive way its molecules absorb infrared light, so it can differentiate between liquid water or vapour and solid ice. Most of the newfound water ice lies in the shadows of craters near the poles, where the warmest temperatures never reach above minus 157 Centigrade. Because of the very small tilt of the Moon's rotation axis, sunlight never reaches these regions. Previous observations indirectly found possible signs of surface ice at the lunar south pole, but these could have been explained by other phenomena, such as unusually reflective lunar soil. With enough ice sitting at the surface -- within the top few millimetres -- water would possibly be accessible as a resource for future expeditions to explore and even stay on the Moon, and potentially easier to access than the water detected beneath the Moon's surface.
INSIGHT PASSES HALWAY POINT TO MARS
NASA
NASA's InSight spacecraft, en route to a Nov. 26 landing on Mars, passed the halfway mark on Aug. 6. All of its instruments have been tested and are working well. The spacecraft has covered 300 million
kilometres since its launch. It will touch down in Mars' Elysium Planitia region, where it will be the first mission to study the Red Planet's deep interior. InSight stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. The InSight team is using the time before the spacecraft's arrival at Mars to not only plan and practice for that critical day, but also to activate and check spacecraft subsystems vital to cruise, landing and surface operations, including the highly sensitive science instruments. InSight's seismometer, which will be used to detect quakes on Mars, received a clean bill of health on July 19. The SEIS instrument (Seismic Experiment for Interior Structure) is a six-sensor seismometer combining two types of sensors to measure ground motions over a wide range of frequencies. It will give scientists a window into Mars' internal activity.
STRUCTURALLY “INSIDE OUT” PLANETARY NEBULA DISCOVERED
The University of Hong Kong
Astronomers have discovered the unusual evolution of the central star of a planetary nebula in our Milky Way. This discovery sheds light on the future evolution, and more importantly, the ultimate fate of the Sun. The research team believes this inverted ionization structure of the nebula is resulted from the central star undergoing a 'born-again' event, ejecting material from its surface and creating a shock that excites the nebular material. Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. As these stars age, they typically strip their outer layers, forming a 'wind'. As the star transitions from its red giant phase to become a white dwarf, it becomes hotter, and starts ionizing the material in the surrounding wind. This causes the gaseous material closer to the star to become highly ionized, while the gas material further out is less so. Studying the planetary nebula HuBi 1 (17,000 light years away and nearly 5 billion years ahead of our solar system in evolution), however, the team found the reverse: HuBi 1's inner regions are less ionized, while the outer regions more so. Analysing the central star, with the participation of top theoretical astrophysicists, the authors found that it is surprisingly cool and metal-rich, and is evolved from a low-mass progenitor star which has a mass 1.1 times of the Sun. The authors suggest that the inner nebula was excited by the passage of a shockwave caused by the star ejecting matter unusually late in its evolution. The stellar material cooled to form circumstellar dust, obscuring the star; this well explains why the central star's optical brightness has diminished rapidly over the past 50 years. In the absence of ionizing photons from the central star, the outer nebula has begun recombining -- becoming neutral. The authors conclude that, as HuBi 1 was roughly the same mass as the Sun, this finding provides a glimpse of a potential future for our solar system.
The discovery resolves a long-lasting question regarding the evolutionary path of metal-rich central stars of planetary nebulae. The team has been observing the evolution of HuBi 1 since 2014 using the Spanish flagship telescope Nordic Optical Telescope and was among the first astrophysicists to discover its inverted ionization structure. After noting HuBi 1's inverted ionization structure and the unusual nature of its central star, astronomers looked closer to find the reasons in collaboration with top theoretical astrophysicists in the world. They came to realize that they had caught HuBi 1 at the exact moment when its central star underwent a brief 'born-again' process to become a hydrogen-poor [WC] and metal-rich star, which is very rare in white dwarf stars evolution. The findings suggest that the Sun may also experience a 'born-again' process while it is dying out in about 5 billion years from now; but way before that event, our Earth will be engulfed by the Sun when it turns into a superhot red giant and nothing living will survive.
WATER WORLDS ARE COMMON
Goldschmidt Conference
Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth. It will have implications for the search of life in our Galaxy. The 1992 discovery of exoplanets orbiting other stars has sparked interest in understanding the composition of these planets to determine, among other goals, whether they are suitable for the development of life. Now a new evaluation of data from the exoplanet-hunting Kepler Space Telescope and the Gaia mission indicates that many of the known planets may contain as much as 50% water. This is much more than the Earth's 0.02% (by weight) water content. Scientists have found that many of the 4000 confirmed or candidate exoplanets discovered so far fall into two size categories: those with the planetary radius averaging around 1.5 that of the Earth, and those averaging around 2.5 times the radius of the Earth. Now a group of scientists, after analyzing the exoplanets with mass measurements and recent radius measurements from the Gaia satellite, have developed a model of their internal structure. The group has looked at how mass relates to radius, and developed a model which might explain the relationship. The model indicates that those exoplanets which have a radius of around x1.5 Earth radius tend to be rocky planets (of typically x5 the mass of the Earth), while those with a radius of x2.5 Earth radius (with a mass around x10 that of the Earth) are probably water worlds.
This is water, but not as commonly found here on Earth. Their surface temperature is expected to be in the 200 to 500 degree Celsius range. Their surface may be shrouded in a water-vapour-dominated atmosphere, with a liquid water layer underneath. Moving deeper, one would expect to find this water transforms into high-pressure ices before we reaching the solid rocky core. The beauty of the model is that it explains just how composition relates to the known facts about these planets. The data indicate that about 35% of all known exoplanets which are bigger than Earth should be water-rich. These water worlds likely formed in similar ways to the giant planet cores (Jupiter, Saturn, Uranus, Neptune) which we find in our own solar system. The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up.
GALAXY CLUSTER HIDING IN PLAIN SIGHT
Massachusetts Institute of Technology
MIT scientists have uncovered a sprawling new galaxy cluster hiding in plain sight. The cluster, which sits 2.4 billion light years from Earth, is made up of hundreds of individual galaxies and surrounds an extremely active supermassive black hole, or quasar. The central quasar is called PKS1353-341 and is intensely bright -- so bright that for decades astronomers observing it in the night sky have assumed that the quasar was quite alone in its corner of the Universe, shining out as a solitary light source from the centre of a single galaxy. The researchers estimate that the cluster is about as massive as 690 trillion suns. Our Milky Way galaxy, for comparison, weighs in at around 400 billion solar masses. The team also calculates that the quasar at the centre of the cluster is 46 billion times brighter than the Sun. Its extreme luminosity is likely the result of a temporary feeding frenzy: As an immense disk of material swirls around the quasar, big chunks of matter from the disk are falling in and feeding it, causing the black hole to radiate huge amounts of energy out as light. This might be a short-lived phase that clusters go through, where the central black hole has a quick meal, gets bright, and then fades away again. Astronomers believe the discovery of this hidden cluster shows there may be other similar galaxy clusters hiding behind extremely bright objects that astronomers have miscatalogued as single light sources. The researchers are now looking for more hidden galaxy clusters, which could be important clues to estimating how much matter there is in the Universe and how fast the Universe is expanding.
In 2012, the team discovered the Phoenix cluster, one of the most massive and luminous galaxy clusters in the Universe. The mystery was why this cluster, which was so intensely bright and in a region of the sky that is easily observable, hadn't been found before. It's because astronomers had preconceived notions of what a cluster should look like. For the most part, astronomers have assumed that galaxy clusters look "fluffy," giving off a very diffuse signal in the X-ray band, unlike brighter, point-like sources, which have been interpreted as extremely active quasars or black holes. The images are either all points, or fluffs, and the fluffs are these giant million-light-year balls of hot gas that we call clusters, and the points are black holes that are accreting gas and glowing as this gas spirals in. The Phoenix discovery proved that galaxy clusters could indeed host immensely active black holes, prompting astronomers to wonder: Could there be other nearby galaxy clusters that were simply misidentified? To answer that question, the researchers set up a survey named CHiPS, for Clusters Hiding in Plain Sight, which is designed to reevaluate X-ray images taken in the past. For every point source that was previously identified, the researchers noted their coordinates and then studied them more directly using the Magellan Telescope, a powerful optical telescope that sits in the mountains of Chile. If they observed a higher-than-expected number of galaxies surrounding the point source (a sign that the gas may stem from a cluster of galaxies), the researchers looked at the source again, using NASA's space-based Chandra X-Ray Observatory, to identify an extended, diffuse source around the main point source. Some 90 percent of these sources turned out to not be clusters. The team plans to comb through more X-ray data in search of galaxy clusters that might have been missed the first time around.
SOME OF THE OLDEST GALAXIES IN UNIVERSE
Durham University
Astronomers from the Institute for Computational Cosmology at Durham University and the Harvard-Smithsonian Center for Astrophysics, have found evidence that the faintest satellite galaxies orbiting our own Milky Way galaxy are amongst the very first galaxies that formed in our Universe. Scientists working on this research have described the finding as "hugely exciting". The research group's findings suggest that galaxies including Segue-1, Bootes I, Tucana II and Ursa Major I are in fact some of the first galaxies ever formed, thought to be over 13 billion years old. When the Universe was about 380,000 years old, the very first atoms formed. These were hydrogen atoms, the simplest element in the periodic table. These atoms collected into clouds and began to cool gradually and settle into the small clumps or "halos" of dark matter that emerged from the Big Bang. This cooling phase, known as the "Cosmic dark ages," lasted about 100 million years. Eventually, the gas that had cooled inside the halos became unstable and began to form stars -- these objects are the very first galaxies ever to have formed. With the formation of the first galaxies, the Universe burst into light, bringing the cosmic dark ages to an end. The team identified two populations of satellite galaxies orbiting the Milky Way.
The first was a very faint population consisting of the galaxies that formed during the "cosmic dark ages." The second was a slightly brighter population consisting of galaxies that formed hundreds of millions of years later, once the hydrogen that had been ionized by the intense ultraviolet radiation emitted by the first stars was able to cool into more massive dark matter halos. Remarkably, the team found that a model of galaxy formation that they had developed previously agreed perfectly with the data, allowing them to infer the formation times of the satellite galaxies. The finding supports the current model for the evolution of our Universe, the 'Lambda-cold-dark-matter model' in which the elementary particles that make up the dark matter drive cosmic evolution. The intense ultraviolet radiation emitted by the first galaxies destroyed the remaining hydrogen atoms by ionizing them (knocking out their electrons), making it difficult for this gas to cool and form new stars. The process of galaxy formation ground to a halt and no new galaxies were able to form for the next billion years or so. Eventually, the halos of dark matter became so massive that even ionized gas was able to cool. Galaxy formation resumed, culminating in the formation of spectacular bright galaxies like our own Milky Way. A decade ago, the faintest galaxies in the vicinity of the Milky Way would have gone under the radar. With the increasing sensitivity of present and future galaxy censuses, a whole new trove of the tiniest galaxies has come into the light, allowing us to test theoretical models in new regimes.
EARLY OPAQUE UNIVERSE LINKED TO GALAXY SCARCITY:
University of California - Riverside
A team of astronomers has made a surprising discovery: 12.5 billion years ago, the most opaque place in the Universe contained relatively little matter. It has long been known that the Universe is filled with a web-like network of dark matter and gas. This "cosmic web" accounts for most of the matter in the Universe, whereas galaxies like our own Milky Way make up only a small fraction. Today, the gas between galaxies is almost totally transparent because it is kept ionized -- electrons detached from their atoms -- by an energetic bath of ultraviolet radiation. Over a decade ago, astronomers noticed that in the very distant past -- roughly 12.5 billion years ago, or about 1 billion years after the Big Bang -- the gas in deep space was not only highly opaque to ultraviolet light, but its transparency varied widely from place to place, obscuring much of the light emitted by distant galaxies. Then a few years ago, a team at the University of Cambridge, found that these differences in opacity were so large that either the amount of gas itself, or more likely the radiation in which it is immersed, must vary substantially from place to place. Today, we live in a fairly homogeneous Universe. If you look in any direction you find, on average, roughly the same number of galaxies and similar properties for the gas between galaxies, the so-called intergalactic gas. At that early time, however, the gas in deep space looked very different from one region of the Universe to another. To find out what created these differences, astronomers turned to one of the largest telescopes in the world: the Subaru telescope on the summit of Mauna Kea in Hawaii. Using its powerful camera, the team looked for galaxies in a vast region, roughly 300 million light years in size, where they knew the intergalactic gas was extremely opaque.
For the cosmic web more opacity normally means more gas, and hence more galaxies. But the team found the opposite: this region contained far fewer galaxies than average. Because the gas in deep space is kept transparent by the ultraviolet light from galaxies, fewer galaxies nearby might make it murkier. Normally it doesn't matter how many galaxies are nearby; the ultraviolet light that keeps the gas in deep space transparent often comes from galaxies that are extremely far away. At this very early time, it looks like the UV light can't travel very far, and so a patch of the Universe with few galaxies in it will look much darker than one with plenty of galaxies around. This discovery may eventually shed light on another phase in cosmic history. In the first billion years after the Big Bang, ultraviolet light from the first galaxies filled the Universe and permanently transformed the gas in deep space. Astronomers believe that this occurred earlier in regions with more galaxies, meaning the large fluctuations in intergalactic radiation may be a relic of this patchy process, and could offer clues to how and when it occurred. By studying both galaxies and the gas in deep space, astronomers hope to get closer to understanding how this intergalactic ecosystem took shape in the early Universe.
ANCIENT QUASARS CONFIRM QUANTUM ENTANGLEMENT
Massachusetts Institute of Technology
Last year, physicists at MIT, the University of Vienna, and elsewhere provided strong support for quantum entanglement, the seemingly far-out idea that two particles, no matter how distant from each other in space and time, can be inextricably linked, in a way that defies the rules of classical physics. Take, for instance, two particles sitting on opposite edges of the Universe. If they are truly entangled, then according to the theory of quantum mechanics their physical properties should be related in such a way that any measurement made on one particle should instantly convey information about any future measurement outcome of the other particle -- correlations that Einstein skeptically saw as "spooky action at a distance." In the 1960s, the physicist John Bell calculated a theoretical limit beyond which such correlations must have a quantum, rather than a classical, explanation. But what if such correlations were the result not of quantum entanglement, but of some other hidden, classical explanation? Such "what-ifs" are known to physicists as loopholes to tests of Bell's inequality, the most stubborn of which is the "freedom-of-choice" loophole: the possibility that some hidden, classical variable may influence the measurement that an experimenter chooses to perform on an entangled particle, making the outcome look quantumly correlated when in fact it isn't. Last February, the MIT team and their colleagues significantly constrained the freedom-of-choice loophole, by using 600-year-old starlight to decide what properties of two entangled photons to measure. Their experiment proved that, if a classical mechanism caused the correlations they observed, it would have to have been set in motion more than 600 years ago, before the stars' light was first emitted and long before the actual experiment was even conceived. Now, the same team has vastly extended the case for quantum entanglement and further restricted the options for the freedom-of-choice loophole. The researchers used distant quasars, one of which emitted its light 7.8 billion years ago and the other 12.2 billion years ago, to determine the measurements to be made on pairs of entangled photons. They found correlations among more than 30,000 pairs of photons, to a degree that far exceeded the limit that Bell originally calculated for a classically based mechanism. If some conspiracy is happening to simulate quantum mechanics by a mechanism that is actually classical, that mechanism would have had to begin its operations -- somehow knowing exactly when, where, and how this experiment was going to be done -- at least 7.8 billion years ago. That seems incredibly implausible, so we have very strong evidence that quantum mechanics is the right explanation. The Earth is about 4.5 billion years old, so any alternative mechanism -- different from quantum mechanics -- that might have produced our results by exploiting this loophole would've had to be in place long before even there was a planet Earth, let alone an MIT. So we've pushed any alternative explanations back to very early in cosmic history.
15 YEARS IN SPACE FOR SPITZER SPACE TELESCOPE
NASA
Initially scheduled for a minimum 2.5-year primary mission, NASA's Spitzer Space Telescope has gone far beyond its expected lifetime -- and is still going strong after 15 years. Launched into a solar orbit on Aug. 25, 2003, Spitzer was the final of NASA's four Great Observatories to reach space. The space telescope has illuminated some of the oldest galaxies in the Universe, revealed a new ring around Saturn, and peered through shrouds of dust to study newborn stars and black holes. Spitzer assisted in the discovery of planets beyond our solar system, including the detection of seven Earth-size planets orbiting the star TRAPPIST-1, among other accomplishments. Spitzer detects infrared light -- most often heat radiation emitted by warm objects. Each of the four Great Observatories collects light in a different wavelength range. By combining their observations of various objects and regions, scientists can gain a more complete picture of the Universe. Spitzer has logged over 106,000 hours of observation time. Thousands of scientists around the world have utilized Spitzer data in their studies, and Spitzer data is cited in more than 8,000 published papers.
Spitzer's primary mission ended up lasting 5.5 years, during which time the spacecraft operated in a "cold phase," with a supply of liquid helium cooling three onboard instruments to just above absolute zero. The cooling system reduced excess heat from the instruments themselves that could contaminate their observations. This gave Spitzer very high sensitivity for "cold" objects. In July 2009, after Spitzer's helium supply ran out, the spacecraft entered a so-called "warm phase." Spitzer's main instrument, called the Infrared Array Camera (IRAC), has four cameras, two of which continue to operate in the warm phase with the same sensitivity they maintained during the cold phase. Spitzer orbits the Sun in an Earth-trailing orbit (meaning it literally trails behind Earth as the planet orbits the Sun) and has continued to fall farther and farther behind Earth during its lifetime. This now poses a challenge for the spacecraft, because while it is downloading data to Earth, its solar panels do not directly face the Sun. As a result, Spitzer must use battery power during data downloads. The batteries are then recharged between downloads. In 2016, Spitzer entered an extended mission dubbed "Spitzer Beyond." The spacecraft is currently scheduled to continue operations into November 2019, more than 10 years after entering its warm phase.
Goldschmidt Conference
The Earth's building blocks seem to be built from 'pretty normal' ingredients, according to researchers working with the world's most powerful telescopes. Scientists have measured the compositions of 18 different planetary systems from up to 456 light years away and compared them to ours, and found that many elements are present in similar proportions to those found on Earth. This is amongst the largest examinations to measure the general composition of materials in other planetary systems, and begins to allow scientists to draw more general conclusions on how they are forged, and what this might mean for finding Earth-like bodies elsewhere. The first planets orbiting other stars were only found in 1992 (this was orbiting a pulsar), since then scientists have been trying to understand whether some of these stars and planets are similar to our own solar system. It is difficult to examine these remote bodies directly. Because of the huge distances involved, their nearby star tends to drown out any electromagnetic signal, such as light or radio waves. Because of this, the team decided to look at how the planetary building blocks affect signals from white dwarf stars. These are stars which have burnt off most of their hydrogen and helium, and shrunk to be very small and dense -- it is anticipated that our Sun will become a white dwarf in around 5 billion years. White dwarfs' atmospheres are composed of either hydrogen or helium, which give out a pretty clear and clean spectroscopic signal. However, as the star cools, it begins to pull in material from the planets, asteroids, comets and so on which had been orbiting it, with some forming a dust disk, a little like the rings of Saturn. As this material approaches the star, it changes how we see the star. This change is measurable because it influences the star's spectroscopic signal, and allows us to identify the type and even the quantity of material surrounding the white dwarf. These measurements can be extremely sensitive, allowing bodies as small as an asteroid to be detected.
The team took measurements using spectrographs on the Keck telescope in Hawaii, the world's largest optical and infrared telescope, and on the Hubble Space Telescope. In this study, the team focused on the sample of white dwarfs with dust disks. Astronomers were able to measure calcium, magnesium, and silicon content in most of these stars, and a few more elements in some stars. They may also have found water in one of the systems, but have not yet quantified it: it's likely that there will be a lot of water in some of these worlds. For example, the team previously identified one star system, 170 light years away in the constellation Boötes, which was rich in carbon, nitrogen and water, giving a composition similar to that of Halley's Comet. In general though, their composition looks very similar to bulk Earth. This would mean that the chemical elements, the building blocks of Earth are common in other planetary systems. From what can be seen, in terms of the presence and proportion of these elements, we're normal, pretty normal. And that means that we can probably expect to find Earth-like planets elsewhere in our Galaxy. This work is still on-going and the recent data release from the Gaia satellite, which so far has characterized 1.7 billion stars, has revolutionized the field. This means we will understand the white dwarfs a lot better. The team hopes to determine the chemical compositions of extrasolar planetary material to a much higher precision.
A GREEN COMET APPROACHES EARTH
Spaceweather.com
Comet 21P/Giacobini-Zinner is approaching Earth. On Sept. 10th, it will be 0.39 AU (58 million km) from our planet and almost bright enough to see with the naked eye. Already it is an easy target for amateur telescopes. This comet is relatively small--its nucleus is barely more than a mile in diameter--but it is bright and active, and a frequent visitor to the inner solar system as it orbits the Sun once every 6.6 years. On Sept. 10th, 21P/Giacobini-Zinner will not only be near Earth, but also at perihelion, its closest approach to the Sun. Solar heating will make it shine like a star of 6th to 7th magnitude, just below the threshold of naked-eye visibility and well within range of common binoculars. 21P/Giacobini-Zinner is the parent of the annual Draconid meteor shower, a bursty display that typically peaks on Oct. 8th. Will the shower will be extra-good this year? Maybe. Draconid outbursts do tend to occur in years near the comet's close approach to the sun. However, not every close approach brings a meteor shower. Forecasters say there are no known Draconid debris streams squarely crossing Earth's path this year, so we will have to wait and see.
ICE CONFIRMED AT MOON’S POLES
NASA/Jet Propulsion Laboratory
In the darkest and coldest parts of its polar regions, a team of scientists has directly observed definitive evidence of water ice on the Moon's surface. These ice deposits are patchily distributed and could possibly be ancient. At the southern pole, most of the ice is concentrated at lunar craters, while the northern pole's ice is more widely, but sparsely spread. A team of scientists used data from NASA's Moon Mineralogy Mapper (M3) instrument to identify three specific signatures that definitively prove there is water ice at the surface of the Moon. M3, aboard the Chandrayaan-1 spacecraft, launched in 2008 by the Indian Space Research Organization, was equipped to confirm the presence of solid ice on the Moon. It collected data that not only picked up the reflective properties we'd expect from ice, but was able to directly measure the distinctive way its molecules absorb infrared light, so it can differentiate between liquid water or vapour and solid ice. Most of the newfound water ice lies in the shadows of craters near the poles, where the warmest temperatures never reach above minus 157 Centigrade. Because of the very small tilt of the Moon's rotation axis, sunlight never reaches these regions. Previous observations indirectly found possible signs of surface ice at the lunar south pole, but these could have been explained by other phenomena, such as unusually reflective lunar soil. With enough ice sitting at the surface -- within the top few millimetres -- water would possibly be accessible as a resource for future expeditions to explore and even stay on the Moon, and potentially easier to access than the water detected beneath the Moon's surface.
INSIGHT PASSES HALWAY POINT TO MARS
NASA
NASA's InSight spacecraft, en route to a Nov. 26 landing on Mars, passed the halfway mark on Aug. 6. All of its instruments have been tested and are working well. The spacecraft has covered 300 million
kilometres since its launch. It will touch down in Mars' Elysium Planitia region, where it will be the first mission to study the Red Planet's deep interior. InSight stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. The InSight team is using the time before the spacecraft's arrival at Mars to not only plan and practice for that critical day, but also to activate and check spacecraft subsystems vital to cruise, landing and surface operations, including the highly sensitive science instruments. InSight's seismometer, which will be used to detect quakes on Mars, received a clean bill of health on July 19. The SEIS instrument (Seismic Experiment for Interior Structure) is a six-sensor seismometer combining two types of sensors to measure ground motions over a wide range of frequencies. It will give scientists a window into Mars' internal activity.
STRUCTURALLY “INSIDE OUT” PLANETARY NEBULA DISCOVERED
The University of Hong Kong
Astronomers have discovered the unusual evolution of the central star of a planetary nebula in our Milky Way. This discovery sheds light on the future evolution, and more importantly, the ultimate fate of the Sun. The research team believes this inverted ionization structure of the nebula is resulted from the central star undergoing a 'born-again' event, ejecting material from its surface and creating a shock that excites the nebular material. Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. As these stars age, they typically strip their outer layers, forming a 'wind'. As the star transitions from its red giant phase to become a white dwarf, it becomes hotter, and starts ionizing the material in the surrounding wind. This causes the gaseous material closer to the star to become highly ionized, while the gas material further out is less so. Studying the planetary nebula HuBi 1 (17,000 light years away and nearly 5 billion years ahead of our solar system in evolution), however, the team found the reverse: HuBi 1's inner regions are less ionized, while the outer regions more so. Analysing the central star, with the participation of top theoretical astrophysicists, the authors found that it is surprisingly cool and metal-rich, and is evolved from a low-mass progenitor star which has a mass 1.1 times of the Sun. The authors suggest that the inner nebula was excited by the passage of a shockwave caused by the star ejecting matter unusually late in its evolution. The stellar material cooled to form circumstellar dust, obscuring the star; this well explains why the central star's optical brightness has diminished rapidly over the past 50 years. In the absence of ionizing photons from the central star, the outer nebula has begun recombining -- becoming neutral. The authors conclude that, as HuBi 1 was roughly the same mass as the Sun, this finding provides a glimpse of a potential future for our solar system.
The discovery resolves a long-lasting question regarding the evolutionary path of metal-rich central stars of planetary nebulae. The team has been observing the evolution of HuBi 1 since 2014 using the Spanish flagship telescope Nordic Optical Telescope and was among the first astrophysicists to discover its inverted ionization structure. After noting HuBi 1's inverted ionization structure and the unusual nature of its central star, astronomers looked closer to find the reasons in collaboration with top theoretical astrophysicists in the world. They came to realize that they had caught HuBi 1 at the exact moment when its central star underwent a brief 'born-again' process to become a hydrogen-poor [WC] and metal-rich star, which is very rare in white dwarf stars evolution. The findings suggest that the Sun may also experience a 'born-again' process while it is dying out in about 5 billion years from now; but way before that event, our Earth will be engulfed by the Sun when it turns into a superhot red giant and nothing living will survive.
WATER WORLDS ARE COMMON
Goldschmidt Conference
Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth. It will have implications for the search of life in our Galaxy. The 1992 discovery of exoplanets orbiting other stars has sparked interest in understanding the composition of these planets to determine, among other goals, whether they are suitable for the development of life. Now a new evaluation of data from the exoplanet-hunting Kepler Space Telescope and the Gaia mission indicates that many of the known planets may contain as much as 50% water. This is much more than the Earth's 0.02% (by weight) water content. Scientists have found that many of the 4000 confirmed or candidate exoplanets discovered so far fall into two size categories: those with the planetary radius averaging around 1.5 that of the Earth, and those averaging around 2.5 times the radius of the Earth. Now a group of scientists, after analyzing the exoplanets with mass measurements and recent radius measurements from the Gaia satellite, have developed a model of their internal structure. The group has looked at how mass relates to radius, and developed a model which might explain the relationship. The model indicates that those exoplanets which have a radius of around x1.5 Earth radius tend to be rocky planets (of typically x5 the mass of the Earth), while those with a radius of x2.5 Earth radius (with a mass around x10 that of the Earth) are probably water worlds.
This is water, but not as commonly found here on Earth. Their surface temperature is expected to be in the 200 to 500 degree Celsius range. Their surface may be shrouded in a water-vapour-dominated atmosphere, with a liquid water layer underneath. Moving deeper, one would expect to find this water transforms into high-pressure ices before we reaching the solid rocky core. The beauty of the model is that it explains just how composition relates to the known facts about these planets. The data indicate that about 35% of all known exoplanets which are bigger than Earth should be water-rich. These water worlds likely formed in similar ways to the giant planet cores (Jupiter, Saturn, Uranus, Neptune) which we find in our own solar system. The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up.
GALAXY CLUSTER HIDING IN PLAIN SIGHT
Massachusetts Institute of Technology
MIT scientists have uncovered a sprawling new galaxy cluster hiding in plain sight. The cluster, which sits 2.4 billion light years from Earth, is made up of hundreds of individual galaxies and surrounds an extremely active supermassive black hole, or quasar. The central quasar is called PKS1353-341 and is intensely bright -- so bright that for decades astronomers observing it in the night sky have assumed that the quasar was quite alone in its corner of the Universe, shining out as a solitary light source from the centre of a single galaxy. The researchers estimate that the cluster is about as massive as 690 trillion suns. Our Milky Way galaxy, for comparison, weighs in at around 400 billion solar masses. The team also calculates that the quasar at the centre of the cluster is 46 billion times brighter than the Sun. Its extreme luminosity is likely the result of a temporary feeding frenzy: As an immense disk of material swirls around the quasar, big chunks of matter from the disk are falling in and feeding it, causing the black hole to radiate huge amounts of energy out as light. This might be a short-lived phase that clusters go through, where the central black hole has a quick meal, gets bright, and then fades away again. Astronomers believe the discovery of this hidden cluster shows there may be other similar galaxy clusters hiding behind extremely bright objects that astronomers have miscatalogued as single light sources. The researchers are now looking for more hidden galaxy clusters, which could be important clues to estimating how much matter there is in the Universe and how fast the Universe is expanding.
In 2012, the team discovered the Phoenix cluster, one of the most massive and luminous galaxy clusters in the Universe. The mystery was why this cluster, which was so intensely bright and in a region of the sky that is easily observable, hadn't been found before. It's because astronomers had preconceived notions of what a cluster should look like. For the most part, astronomers have assumed that galaxy clusters look "fluffy," giving off a very diffuse signal in the X-ray band, unlike brighter, point-like sources, which have been interpreted as extremely active quasars or black holes. The images are either all points, or fluffs, and the fluffs are these giant million-light-year balls of hot gas that we call clusters, and the points are black holes that are accreting gas and glowing as this gas spirals in. The Phoenix discovery proved that galaxy clusters could indeed host immensely active black holes, prompting astronomers to wonder: Could there be other nearby galaxy clusters that were simply misidentified? To answer that question, the researchers set up a survey named CHiPS, for Clusters Hiding in Plain Sight, which is designed to reevaluate X-ray images taken in the past. For every point source that was previously identified, the researchers noted their coordinates and then studied them more directly using the Magellan Telescope, a powerful optical telescope that sits in the mountains of Chile. If they observed a higher-than-expected number of galaxies surrounding the point source (a sign that the gas may stem from a cluster of galaxies), the researchers looked at the source again, using NASA's space-based Chandra X-Ray Observatory, to identify an extended, diffuse source around the main point source. Some 90 percent of these sources turned out to not be clusters. The team plans to comb through more X-ray data in search of galaxy clusters that might have been missed the first time around.
SOME OF THE OLDEST GALAXIES IN UNIVERSE
Durham University
Astronomers from the Institute for Computational Cosmology at Durham University and the Harvard-Smithsonian Center for Astrophysics, have found evidence that the faintest satellite galaxies orbiting our own Milky Way galaxy are amongst the very first galaxies that formed in our Universe. Scientists working on this research have described the finding as "hugely exciting". The research group's findings suggest that galaxies including Segue-1, Bootes I, Tucana II and Ursa Major I are in fact some of the first galaxies ever formed, thought to be over 13 billion years old. When the Universe was about 380,000 years old, the very first atoms formed. These were hydrogen atoms, the simplest element in the periodic table. These atoms collected into clouds and began to cool gradually and settle into the small clumps or "halos" of dark matter that emerged from the Big Bang. This cooling phase, known as the "Cosmic dark ages," lasted about 100 million years. Eventually, the gas that had cooled inside the halos became unstable and began to form stars -- these objects are the very first galaxies ever to have formed. With the formation of the first galaxies, the Universe burst into light, bringing the cosmic dark ages to an end. The team identified two populations of satellite galaxies orbiting the Milky Way.
The first was a very faint population consisting of the galaxies that formed during the "cosmic dark ages." The second was a slightly brighter population consisting of galaxies that formed hundreds of millions of years later, once the hydrogen that had been ionized by the intense ultraviolet radiation emitted by the first stars was able to cool into more massive dark matter halos. Remarkably, the team found that a model of galaxy formation that they had developed previously agreed perfectly with the data, allowing them to infer the formation times of the satellite galaxies. The finding supports the current model for the evolution of our Universe, the 'Lambda-cold-dark-matter model' in which the elementary particles that make up the dark matter drive cosmic evolution. The intense ultraviolet radiation emitted by the first galaxies destroyed the remaining hydrogen atoms by ionizing them (knocking out their electrons), making it difficult for this gas to cool and form new stars. The process of galaxy formation ground to a halt and no new galaxies were able to form for the next billion years or so. Eventually, the halos of dark matter became so massive that even ionized gas was able to cool. Galaxy formation resumed, culminating in the formation of spectacular bright galaxies like our own Milky Way. A decade ago, the faintest galaxies in the vicinity of the Milky Way would have gone under the radar. With the increasing sensitivity of present and future galaxy censuses, a whole new trove of the tiniest galaxies has come into the light, allowing us to test theoretical models in new regimes.
EARLY OPAQUE UNIVERSE LINKED TO GALAXY SCARCITY:
University of California - Riverside
A team of astronomers has made a surprising discovery: 12.5 billion years ago, the most opaque place in the Universe contained relatively little matter. It has long been known that the Universe is filled with a web-like network of dark matter and gas. This "cosmic web" accounts for most of the matter in the Universe, whereas galaxies like our own Milky Way make up only a small fraction. Today, the gas between galaxies is almost totally transparent because it is kept ionized -- electrons detached from their atoms -- by an energetic bath of ultraviolet radiation. Over a decade ago, astronomers noticed that in the very distant past -- roughly 12.5 billion years ago, or about 1 billion years after the Big Bang -- the gas in deep space was not only highly opaque to ultraviolet light, but its transparency varied widely from place to place, obscuring much of the light emitted by distant galaxies. Then a few years ago, a team at the University of Cambridge, found that these differences in opacity were so large that either the amount of gas itself, or more likely the radiation in which it is immersed, must vary substantially from place to place. Today, we live in a fairly homogeneous Universe. If you look in any direction you find, on average, roughly the same number of galaxies and similar properties for the gas between galaxies, the so-called intergalactic gas. At that early time, however, the gas in deep space looked very different from one region of the Universe to another. To find out what created these differences, astronomers turned to one of the largest telescopes in the world: the Subaru telescope on the summit of Mauna Kea in Hawaii. Using its powerful camera, the team looked for galaxies in a vast region, roughly 300 million light years in size, where they knew the intergalactic gas was extremely opaque.
For the cosmic web more opacity normally means more gas, and hence more galaxies. But the team found the opposite: this region contained far fewer galaxies than average. Because the gas in deep space is kept transparent by the ultraviolet light from galaxies, fewer galaxies nearby might make it murkier. Normally it doesn't matter how many galaxies are nearby; the ultraviolet light that keeps the gas in deep space transparent often comes from galaxies that are extremely far away. At this very early time, it looks like the UV light can't travel very far, and so a patch of the Universe with few galaxies in it will look much darker than one with plenty of galaxies around. This discovery may eventually shed light on another phase in cosmic history. In the first billion years after the Big Bang, ultraviolet light from the first galaxies filled the Universe and permanently transformed the gas in deep space. Astronomers believe that this occurred earlier in regions with more galaxies, meaning the large fluctuations in intergalactic radiation may be a relic of this patchy process, and could offer clues to how and when it occurred. By studying both galaxies and the gas in deep space, astronomers hope to get closer to understanding how this intergalactic ecosystem took shape in the early Universe.
ANCIENT QUASARS CONFIRM QUANTUM ENTANGLEMENT
Massachusetts Institute of Technology
Last year, physicists at MIT, the University of Vienna, and elsewhere provided strong support for quantum entanglement, the seemingly far-out idea that two particles, no matter how distant from each other in space and time, can be inextricably linked, in a way that defies the rules of classical physics. Take, for instance, two particles sitting on opposite edges of the Universe. If they are truly entangled, then according to the theory of quantum mechanics their physical properties should be related in such a way that any measurement made on one particle should instantly convey information about any future measurement outcome of the other particle -- correlations that Einstein skeptically saw as "spooky action at a distance." In the 1960s, the physicist John Bell calculated a theoretical limit beyond which such correlations must have a quantum, rather than a classical, explanation. But what if such correlations were the result not of quantum entanglement, but of some other hidden, classical explanation? Such "what-ifs" are known to physicists as loopholes to tests of Bell's inequality, the most stubborn of which is the "freedom-of-choice" loophole: the possibility that some hidden, classical variable may influence the measurement that an experimenter chooses to perform on an entangled particle, making the outcome look quantumly correlated when in fact it isn't. Last February, the MIT team and their colleagues significantly constrained the freedom-of-choice loophole, by using 600-year-old starlight to decide what properties of two entangled photons to measure. Their experiment proved that, if a classical mechanism caused the correlations they observed, it would have to have been set in motion more than 600 years ago, before the stars' light was first emitted and long before the actual experiment was even conceived. Now, the same team has vastly extended the case for quantum entanglement and further restricted the options for the freedom-of-choice loophole. The researchers used distant quasars, one of which emitted its light 7.8 billion years ago and the other 12.2 billion years ago, to determine the measurements to be made on pairs of entangled photons. They found correlations among more than 30,000 pairs of photons, to a degree that far exceeded the limit that Bell originally calculated for a classically based mechanism. If some conspiracy is happening to simulate quantum mechanics by a mechanism that is actually classical, that mechanism would have had to begin its operations -- somehow knowing exactly when, where, and how this experiment was going to be done -- at least 7.8 billion years ago. That seems incredibly implausible, so we have very strong evidence that quantum mechanics is the right explanation. The Earth is about 4.5 billion years old, so any alternative mechanism -- different from quantum mechanics -- that might have produced our results by exploiting this loophole would've had to be in place long before even there was a planet Earth, let alone an MIT. So we've pushed any alternative explanations back to very early in cosmic history.
15 YEARS IN SPACE FOR SPITZER SPACE TELESCOPE
NASA
Initially scheduled for a minimum 2.5-year primary mission, NASA's Spitzer Space Telescope has gone far beyond its expected lifetime -- and is still going strong after 15 years. Launched into a solar orbit on Aug. 25, 2003, Spitzer was the final of NASA's four Great Observatories to reach space. The space telescope has illuminated some of the oldest galaxies in the Universe, revealed a new ring around Saturn, and peered through shrouds of dust to study newborn stars and black holes. Spitzer assisted in the discovery of planets beyond our solar system, including the detection of seven Earth-size planets orbiting the star TRAPPIST-1, among other accomplishments. Spitzer detects infrared light -- most often heat radiation emitted by warm objects. Each of the four Great Observatories collects light in a different wavelength range. By combining their observations of various objects and regions, scientists can gain a more complete picture of the Universe. Spitzer has logged over 106,000 hours of observation time. Thousands of scientists around the world have utilized Spitzer data in their studies, and Spitzer data is cited in more than 8,000 published papers.
Spitzer's primary mission ended up lasting 5.5 years, during which time the spacecraft operated in a "cold phase," with a supply of liquid helium cooling three onboard instruments to just above absolute zero. The cooling system reduced excess heat from the instruments themselves that could contaminate their observations. This gave Spitzer very high sensitivity for "cold" objects. In July 2009, after Spitzer's helium supply ran out, the spacecraft entered a so-called "warm phase." Spitzer's main instrument, called the Infrared Array Camera (IRAC), has four cameras, two of which continue to operate in the warm phase with the same sensitivity they maintained during the cold phase. Spitzer orbits the Sun in an Earth-trailing orbit (meaning it literally trails behind Earth as the planet orbits the Sun) and has continued to fall farther and farther behind Earth during its lifetime. This now poses a challenge for the spacecraft, because while it is downloading data to Earth, its solar panels do not directly face the Sun. As a result, Spitzer must use battery power during data downloads. The batteries are then recharged between downloads. In 2016, Spitzer entered an extended mission dubbed "Spitzer Beyond." The spacecraft is currently scheduled to continue operations into November 2019, more than 10 years after entering its warm phase.
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Windows PCs & Software: Help, News & Discussion / Re: How to record Webcast
« Last post by Simon on September 14, 2018, 21:13 »6
Windows PCs & Software: Help, News & Discussion / How to record Webcast
« Last post by Den on September 14, 2018, 20:53 »I need to record two Webcasts of the planning committee meetings and save them on my computer (or Cloud).
What is the best way to do this with Windows 10?
What is the best way to do this with Windows 10?
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The Buzz / Re: Radio 2 in the mornings.
« Last post by Clive on September 03, 2018, 16:22 »Fantastic news! I've always detested him.
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The Buzz / Radio 2 in the mornings.
« Last post by Den on September 03, 2018, 10:18 »Radio 2 in the mornings.
Chris Evans to leave BBC morning radio.
Hopefully I will be able to tune into Radio 2 on the way to work again after December.
Chris Evans to leave BBC morning radio.
Hopefully I will be able to tune into Radio 2 on the way to work again after December.
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Hobbies & Crafts / Re: Cadwell Park
« Last post by GillE on August 22, 2018, 13:54 »If I ever find a moto-cross or scrambling event near me, I'll be there! It must be quite a spectacle in its own right and great for photographers.