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Mid December Astronomy Bulletin
« on: December 13, 2020, 11:58 »
Harvard-Smithsonian Center for Astrophysics

Scientists have identified a problem with the growing interest in extractable resources on the Moon: there aren't enough of them to go around. With no international policies or agreements to decide "who gets what from where," scientists believe tensions, overcrowding, and quick exhaustion of resources to be one possible future for Moon mining projects. Resources like water and iron are important because they will enable future research to be conducted on, and launched from, the Moon. Interest in the Moon as a location for extracting resources isn't new. An extensive body of research dating back to the Apollo program has explored the availability of resources such as helium, water, and iron, with more recent research focusing on continuous access to solar power, cold traps and frozen water deposits, and even volatiles that may exist in shaded areas on the surface of the moon. Although some treaties do exist, like the 1967 Outer Space Treaty -- prohibiting national appropriation -- and the 2020 Artemis Accords --reaffirming the duty to coordinate and notify -- neither is meant for robust protection.  Much of the discussion surrounding the Moon, and including current and potential policy for governing missions to the satellite, have centered on scientific versus commercial activity, and who should be allowed to tap into the resources locked away in, and on, the Moon.

There is still a risk that resource locations will turn out to be more scant than currently believed, and scientists want to go back and get a clearer picture of resource availability before anyone starts digging, drilling, or collecting. While more research on these lunar hot spots is needed to inform policy, the framework for possible solutions to potential crowding are already in view. One of the first challenges for policymakers will be to characterize the resources at stake at each individual site. Are these resources, say, areas of real estate at the high-value Peaks of Eternal Light, where the Sun shines almost continuously, or are they units of energy to be generated from solar panels installed there? At what level can they realistically be exploited? How should the benefits from those activities be distributed?  Developing agreement on those questions is a likely precondition to the successful coordination of activities at these uniquely attractive lunar sites.

Association of Universities for Research in Astronomy (AURA)

A team of astronomers has discovered that CK Vulpeculae, first seen as a bright new star in 1670, is approximately five times farther away than previously thought. This makes the 1670 explosion of CK Vulpeculae much more energetic than previously estimated and puts it into a mysterious class of objects that are too bright to be members of the well-understood type of explosions known as novae, but too faint to be supernovae. 350 years ago, the French monk Anthelme Voituret saw a bright new star flare into life in the constellation of Vulpecula. Over the following months, the star became almost as bright as Polaris (the North Star) and was monitored by some of the leading astronomers of the day before it faded from view after a year. The new star eventually gained the name CK Vulpeculae and was long considered to be the first documented example of a nova -- a fleeting astronomical event arising from an explosion in a close binary star system in which one member is a white dwarf, the remnant of a Sun-like star. However, a string of recent results have thrown the longstanding classification of CK Vulpeculae as a nova into doubt. 17th-century astronomers who observed the bright new star CK Vulpeculae included distinguished Polish mayor, brewer, and astronomer Johannes
Hevelius and the French-Italian astronomer Giovanni Domenico Cassini, who discovered four of Saturn's moons. After it faded from view in 1671 there were numerous unsuccessful attempts through the intervening centuries to recover it, some by noted astronomers including Halley, Pickering and Humason.

In 2015, a team of astronomers suggested that CK Vulpeculae's appearance in 1670 was the result of two normal stars undergoing a cataclysmic collision. Just over three years later, the same astronomers further proposed that one of the stars was in fact a bloated red giant star, following their discovery of a radioactive isotope of aluminium in the immediate surroundings of the site of the 1670 explosion. Complicating the picture even further, a separate group of astronomers proposed a different interpretation. In their paper, also published in 2018, they suggested that the sudden brightening in 1670 was the result of the merger between a brown dwarf -- a failed star too small to shine via thermonuclear fusion that powers the Sun -- and a white dwarf. Now, adding to the ongoing mystery surrounding CK Vulpeculae, new observations from the international Gemini Observatory, a Program of NSF's NOIRLab, reveal that this enigmatic astronomical object is much farther away and has ejected gas at much higher speeds than previously reported. This team initially planned to use the Gemini Near-Infrared Spectrograph (GNIRS) instrument on Gemini North on Hawai'i's Maunakea to confirm the 2018 detection of radioactive aluminium at the heart of CK Vulpeculae. After realizing that detecting this in the infrared would be far more difficult than they originally thought, the astronomers improvised and obtained infrared observations across the full extent of CK Vulpeculae, including the two wisps of nebulosity at its outermost edges. By measuring both the speed of the nebula's expansion and how much the outermost wisps had moved during the last ten years, and accounting for the tilt of the nebula on the night sky, which had been estimated earlier by others, the team determined that CK Vulpeculae lies approximately 10,000 light-years distant from the Sun --about five times as far away as previously thought. That implies that the 1670 explosion was far brighter, releasing roughly 25 times more energy than previously estimated. This much larger estimate of the amount of energy released means that whatever event caused the sudden appearance of CK Vulpeculae in 1670 was far more violent than a simple nova. In terms of energy released, the finding places CKVulpeculae roughly midway between a nova and a supernova. It is one of a very few such objects in the Milky Way and the cause -- or causes -- of the outbursts of this intermediate class of objects remain unknown. I think we all know what CK Vulpeculae isn't, but no one knows what it is. The visual appearance of the CK Vulpeculae nebula and the high velocities observed by the team could help astronomers to recognize relics of similar events -- in our Milky Way or in external galaxies -- that have occurred in the past.

University of Washington

Stars can live for billions of years, and they typically make slow transitions -- sometimes over many millions of years -- between the different stages of their lives.  So when a previously typical star's behaviour rapidly changes in a few decades, astronomers take note and get to work. Such is the case with a star known as SAO 244567, which lies at the centre of Hen 3-1357, commonly known as the Stingray Nebula. The Stingray Nebula is a planetary nebula -- an expanse of material sloughed off from a star as it enters a new phase of old age and then heated by that same star into colourful displays that can last for up to a million years. The tiny Stingray Nebula unexpectedly appeared in the 1980s and was first imaged by scientists in the 1990s using NASA's Hubble Space Telescope. It is by far the youngest planetary nebula in our sky. A team of astronomers recently analyzed a more recent image of the nebula, taken in 2016 by Hubble, and found something unexpected. The Stingray Nebula has faded significantly and changed shape over the course of just 20 years. If dimming continues at current rates, in 20 or 30 years the Stingray Nebula will be barely perceptible, and was likely already fading when Hubble obtained the first clear images of it in 1996. Planetary nebulae form after most stars, including stars like our own Sun, swell into red giants as they exhaust hydrogen fuel. At the end of the red giant phase, the star then expels large amounts of its outer material as it gradually -- over the course of a million years -- transforms into a small, compact white dwarf. The sloughed-off material expands outward for several thousand years while the star heats the material, which eventually becomes ionized and glows.

Astronomers compared Hubble images of the Stingray Nebula taken in 1996 and 2016. Hen 3-1357 changed shape markedly over 20 years, losing the sharp, sloping edges that gave the Stingray Nebula its name. Its colours have faded overall and once-prominent blue expanses of gas near its centre are largely gone. The team analyzed light spectra from Hen 3-1357 emitted by chemical elements in the nebula. Emission levels of hydrogen, nitrogen, sulphur and oxygen all dropped between 1996 and 2016, particularly oxygen, which dropped by a factor of 900. The resulting fade in colour and the nebula's change in shape are likely connected to the cooling of its parent star -- from a peak of about 60,000 degrees centigrade in 2002 to 50,000 degrees centigrade in 2015 -- which means it is giving off less ultraviolet ionizing radiation that heats the expelled gas and makes it glow. Astronomers have
yet to understand why SAO 244567 made the Stingray Nebula light up and then fade almost as quickly. One theory is that the star underwent a brief burst of fresh helium fusion around its core, which stirred up its outer layers and caused its surface to both shrink and heat. If so, then as its outer layers settle back down, the star may return to a more typical transition from red giant to white dwarf. Only future observations of the star and its nebula can confirm this.

National Observatory of Japan

A new map of the Milky Way has put Earth 2000 light years closer to the supermassive black hole at the centre of our galaxy. This map has suggested that the centre of the Milky Way, and the black hole which sits there, is located 25,800 light-years from Earth. This is closer than the official value of 27,700 light-years adopted by the International Astronomical Union in 1985. What's more, according to the map, our solar system is travelling at 227 kilometres per second as it orbits around the galactic centre -- this is faster than the official value of 220 kilometres per second. These updated values are a result of more than 15 years of observations by the Japanese radio astronomy project VERA, according to an announcement released Thursday from the National Observatory of Japan. VERA is short for VLBI Exploration of Radio Astrometry and refers to the mission's array of telescopes, which use Very Long Baseline Interferometry to explore the three-dimensional structure of the Milky Way.

Because the Earth is located inside the Milky Way, it's difficult to step back and see what the galaxy looks like. To get around this, the project used astrometry, the accurate measurement of the position and motion of objects, to understand the overall structure of the Milky Way and Earth's place in it. The black hole is known as Sagittarius A* or Sgr A* and is 4.2 million times more massive than our Sun. The supermassive hole and its enormous gravitational field governs the orbits of stars at the centre of the Milky Way. There are several types of black holes, and scientists believe the supermassive ones may be connected to the formation of galaxies, as they often exist at the centre of the massive star systems -- but it's still not clear exactly how, or which form first.

University of Edinburgh

The long-held belief that the Milky Way, the galaxy containing Earth and the solar system, is relatively static has been ruptured by fresh cosmic insight. The spiral-shaped disc of stars and planets is being pulled, twisted and deformed with extreme violence by the gravitational force of a smaller galaxy -- the Large Magellanic Cloud (LMC). Scientists believe the LMC crossed the Milky Way's boundary around 700 million years ago -- recent by cosmological standards -- and due to its large dark matter content it strongly upset our galaxy's fabric and motion as it fell in. The effects are still being witnessed today and should force a revision of how our galaxy evolved, astronomers say. The LMC, now a satellite galaxy of the Milky Way, is visible as a faint cloud in the southern hemisphere's night skies -- as observed by its namesake, the 16th century Portuguese explorer Ferdinand Magellan. Previous research has revealed that the LMC, like the Milky Way, is surrounded by a halo of dark matter -- elusive particles which surround galaxies and do not absorb or emit light but have dramatic gravitational effects on the movement of stars and gas in the Universe. Using a sophisticated statistical model that calculated the speed of the Milky Way's most distant stars, the University of Edinburgh team discovered how the LMC warped our galaxy's motion. The researchers found that the enormous attraction of the LMC's dark matter halo is pulling and twisting the Milky Way disc at 32 km/s towards the constellation Pegasus. To their surprise they also found that the Milky Way was not moving towards the LMC's current location, as previously thought, but towards a point in its past trajectory. They believe this is because the LMC, powered by its massive gravitational force, is moving away from the Milky Way at the even faster speed of 370 km/s. Astronomers say it is as if the Milky Way is trying hard to hit a fast moving target, but not aiming very well. This discovery will help scientists develop new modelling techniques that capture the strong dynamic interplay between the two galaxies. Astronomers now intend to find out the direction from which the LMC first fell in to the Milky Way and the exact time it happened. This will reveal the amount and distribution of dark matter in the Milky Way and the LMC with unprecedented detail.


An international team of astronomers has announced the most detailed ever catalogue of the stars in a huge swathe of our Milky Way galaxy. The measurements of stellar position and movement in the third data release from the European Space Agency’s Gaia space observatory, will then be publicly available. Initial findings include the first optical measurement of the acceleration of the Solar system.  Launched in 2013, Gaia operates in an orbit around the so-called Lagrange 2 (L2) point, located 1.5 million kilometres behind the Earth in the direction away from the Sun. At L2 the gravitational forces between the Earth and Sun are balanced, so the spacecraft stays in stable position, allowing long-term essentially unobstructed views of the sky. The primary objective of Gaia is measuring stellar distances using the parallax method. In this case astronomers use the observatory to continuously scan the sky, measuring the apparent change in the positions of stars over time, resulting from the Earth’s movement around the Sun. Knowing that tiny shift in the positions of stars allows their distances to be calculated. On Earth this is made more difficult by the blurring of the Earth’s atmosphere, but in space the measurements are only limited by the optics of the telescope. Two previous releases included the positions of 1.6 billion stars. This release brings the total to just under 2 billion stars, whose positions are significantly more accurate than in the earlier data. Gaia also tracks the changing positions of the stars over time across the line of sight (their so-called proper motion), and by splitting their light into spectra, measures how fast they are moving towards or away from the Sun and assesses their chemical composition.

The new data include exceptionally accurate measurements of the 300,000 stars within the closest 326 light years to the Sun. The researchers use these data to predict how the star background will change in the next 1.6 million years. They also confirm that the Solar system is accelerating in its orbit around the Galaxy. This acceleration is gentle, and is what would be expected from a system in a circular orbit. Over a year the Sun accelerates towards the centre of the Galaxy by 7 mm per second, compared with its speed along its orbit of about 200 kilometres a second. Gaia data additionally deconstruct the two largest companion galaxies to the Milky Way, the Small and Large Magellanic Clouds, allowing researchers to see their different stellar populations. A dramatic visualisation shows these subsets, and the bridge of stars between the two systems. Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres. These data are one of the backbones of astrophysics, allowing us to forensically analyse our stellar neighbourhood, and tackle crucial questions about the origin and future of our Galaxy. Gaia will continue gathering data until at least 2022, with a possible mission extension until 2025. The final data releases are expected to yield stellar positions 1.9 times as accurate as those released so far, and proper motions more than 7 times more accurate, in a catalogue of more than 2 billion objects.

University of Kansas

Researchers have described a galaxy more than 5.25 billion light years away undergoing a rarely seen stage in its galactic life cycle. The galaxy, dubbed CQ 4479, shows characteristics that normally don't coexist: an X-ray luminous active galactic nuclei (AGN) and a cold gas supply fuelling high star formation rates. Massive galaxies, such as our own Milky Way, host a supermassive black hole at
their hearts -- these are black holes that grow by accreting interstellar gas onto themselves to become more massive. The end of galactic growth is thought to happen when this gas accretion onto the black hole occurs in sufficient quantities that it produces a tremendous amount of energy. Then, all of that energy surrounding the black hole will actually heat up the rest of the gas throughout the galaxy in such a way that it can't condense any more to form stars and the galaxy's growth stops. The researchers instead found CQ 4479, a galaxy which never had been closely studied before, to be still generating new stars in spite of the luminous AGN at the galaxy's centre. The researchers observed the cold quasar primarily using NASA's SOFIA infrared telescope, which is flown aboard a Boeing 747 aircraft. Other measurements were made using FUV-FIR photometry and optical spectroscopy. What's really unique about this source is astronomers have different measurements of the energy output near the black hole. That reveals how fast the black hole is growing and also its feedback into the host galaxy that can shut down star formation.  We have everything from X-ray, to optical and the infrared, so researchers were able to measure several different signatures of the black hole's energy output. And the signatures don't agree -- that's really rare. One interpretation is the growth of the black hole is slowing, because the X-rays come from right next to the black hole, while the optical signatures come from a little bit further out, and the infrared signatures come from further out as well. Essentially, less energy seems to be being produced right around the black hole now than it was in the past.

The researchers seem to be looking at a snapshot of the galaxy during a pivotal stage of its lifespan. Other questions about the physical structure of the galaxy remain because current instrumentation available to astronomers don't provide clear enough images of CQ 4479. The image we have shows a central blob and then a little smaller blob below it. So we don't have a good sense for how this galaxy looks because the central AGN is so bright that it outshines the rest of the host galaxy. This is a real problem that plagues all AGN studies -- when you're dealing with the most luminous things they tend to outshine your host at nearly every wavelength. The researchers said CQ 4479 would require more study, particularly using the ALMA Observatory and the NASA's James Webb Space Telescope -- the most powerful space telescope ever designed and currently slated for launch Oct. 31, 2021. The importance of understanding the strange processes underway in a galaxy 5.25 billion light years from Earth might seem vague at first, but a better understanding of the cold quasar could improve understanding of the cosmos and the fate of our own galaxy.

Kavli Institute for the Physics and Mathematics of the Universe

Using Planck data from the cosmic microwave background radiation, researchers have observed a hint of new physics. The team developed a new method to measure the polarization angle of the ancient light by calibrating it with dust emission from our own Milky Way. While the signal is not detected with enough precision to draw definite conclusions, it may suggest that dark matter or dark energy causes a violation of the so-called "parity symmetry." The laws of physics governing the Universe are thought not to change when flipped around in a mirror. For example, electromagnetism works the same regardless of whether you are in the original system, or in a mirrored system in which all spatial coordinates have been flipped. If this symmetry, called "parity," is violated, it may hold the key to understanding the elusive nature of dark matter and dark energy, which occupy 25 and 70 percent of the energy budget of the Universe today, respectively. While both dark, these two components have opposite effects on the evolution of the Universe: dark matter attracts, while dark energy causes the Universe to expand ever faster. A new study, including researchers from the Institute of Particle and Nuclear Studies (IPNS) at the High Energy Accelerator Research Organization (KEK), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) of the University of Tokyo, and the Max Planck Institute for Astrophysics (MPA), reports on a tantalizing hint of new physics -- with 99.2 percent confidence level -- which violates parity symmetry. The hint to a violation of parity symmetry was found in the cosmic microwave background radiation, the remnant light of the Big Bang. The key is the polarized light of the cosmic microwave background. Light is a propagating electromagnetic wave. When it consists of waves oscillating in a preferred direction, physicists call it "polarized." The polarization arises when the light is scattered.

Sunlight, for instance, consists of waves with all possible oscillating directions; thus, it is not polarized. The light of a rainbow, meanwhile, is polarized because the sunlight is scattered by water droplets in the atmosphere. Similarly, the light of the cosmic microwave background initially became polarized when scattered by electrons 400,000 years after the Big Bang. As this light travelled through the Universe for 13.8 billion years, the interaction of the cosmic microwave background with dark matter or dark energy could cause the plane of polarization to rotate by an angle. To measure the rotation angle, the scientists needed polarization-sensitive detectors, such as those onboard the Planck satellite of the European Space Agency (ESA). And they needed to know how the polarization-sensitive detectors are oriented relative to the sky. If this information was not known with sufficient precision, the measured polarization plane would appear to be rotated artificially, creating a false signal. In the past, uncertainties over the artificial rotation introduced by the detectors themselves limited the measurement accuracy of the cosmic polarization angle. The distance travelled by the light from dust within the Milky Way is much shorter than that of the cosmic microwave background. This means that the dust emission is not affected by dark matter or dark energy, i.e. (the polarization angle) is present only in the light of the cosmic microwave background, while the artificial rotation affects both. The difference in the measured polarization angle between both sources of light can thus be used to measure (the angle). The research team applied the new method to measure (the angle) from the polarization data taken by the Planck satellite. They found a hint for violation of parity symmetry
with 99.2 percent confidence level. To claim a discovery of new physics, much greater statistical significance, or a confidence level of 99.99995 percent, is required. To confirm this signal, the new method can be applied to any of the existing -- and future -- experiments measuring polarization of the cosmic microwave background, such as Simons Array and LiteBIRD, in which both KEK and the Kavli IPMU are involved.

Georgetown University Medical Center

Studies of both mice and humans who have travelled into space reveal that critical parts of a cell's energy production machinery, the mitochondria, can be made dysfunctional due to changes in gravity, radiation exposure and other factors, according to investigators at Georgetown Lombardi Comprehensive Cancer Center.  These findings are part of an extensive research effort across many scientific disciplines to look at the health effects of travel into space. The research has implications for future space travel as well as how metabolic changes due to space travel could inform medical science on Earth. The group's research efforts centred around muscle tissue from mice that were sent into space and were compared with analyses by other scientists who studied different mouse tissue. Although each studied different tissue, they all came to the same conclusion: that mitochondrial
function was adversely impacted by space travel. In addition to studying the effects of space travel on cellular function, the scientists used a trove of data from decades of NASA human flight experiments to correlate their outcomes in animals with those from 59 astronauts. They were also able to access data derived from NASA's repository of biospecimens that had flown in space to do further comparisons. Data from NASA's Twin Study of Mark and Scott Kelly was particularly informative as it allowed for a comparison of the health effects seen in an astronaut in space, Scott, with his earth-bound brother, Mark, who is a retired astronaut. Comparing their studies of mice with human data, Laiakis and the team of researchers were able to determine that space travel led to certain metabolic effects:

• Isolated cells were adversely impacted to a higher degree than whole organs
• Changes in the liver were more noticeable than in other organs
• Mitochondrial function was impacted

Because space travel almost always exposes people to higher levels of radiation than would be found on earth, the scientists knew that such an exposure could harm mitochondria. This aspect of radiation exposure translates to health outcomes here on Earth for cancer patients who undergo radiotherapy. With this knowledge of radiation's impact on mitochondria, clinicians might tailor radiation therapy in different ways in the future to protect normal tissue. The implications for travel to Mars are especially concerning, the researchers say, as that would involve a much longer time in space and hence lengthy exposure to radiation.

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