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February 23, 2020 at 5:11 am #10016Anonymous
THE SOCIETY FOR POPULAR ASTRONOMY Electronic News Bulletin No. 509 2020 Feb 23
Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is arguably Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a
secure server or just see how much we have to offer by visiting http://www.popastro.com
CHEMISTRY OF MOON'S SOIL
Back in 1972, NASA sent their last team of astronauts to the Moon in the Apollo 17 mission. These astronauts brought some of the Moon back to Earth so scientists could continue to study lunar soil in their labs. Since we haven't returned to the Moon in almost 50 years, every lunar sample is precious. We need to make them count for researchers now and in the future. In a new study, scientists found a new way to analyze the chemistry of the Moon's soil using a single grain of dust. Their technique can help us learn more about conditions on the surface of the Moon and formation of precious resources like water and helium there. The technique is called atom probe tomography (APT), and it's normally used by materials scientists working to improve industrial processes like making steel and nanowires. But its ability to analyze tiny amounts of materials makes it a good candidate for studying lunar samples. The Apollo 17 sample contains 111 kilograms of lunar rocks and soil — in the grand scheme of things, not a lot, so researchers have to use it wisely. The analysis only required one single grain of soil, about as wide as a human hair. In that tiny grain, researchers identified products of space weathering, pure iron, water and helium, that formed through the interactions of the lunar soil with the
space environment. Extracting these precious resources from lunar soil could help future astronauts sustain their activities on the Moon. To study the tiny grain, the team used a focused beam of charged atoms to carve a tiny, super-sharp tip into its surface. This tip was only a few hundred atoms wide
— for comparison, a sheet of paper is hundreds of thousands of atoms thick.
Once the sample was inside the atom probe at Northwestern University, it was zapped it with a laser to knock atoms off one by one. As the atoms flew off the sample, they struck a detector plate. Heavier elements, like iron, take longer to reach the detector than lighter elements, like hydrogen. By
measuring the time between the laser firing and the atom striking the detector, the instrument is able to determine the type of atom at that position and its charge. Finally, the data were reconstructed in three
dimensions, using a colour-coded point for each atom and molecule to make a nanoscale 3D map of the Moon dust. It's the first time scientists can see both the type of atoms and their exact location in a speck of lunar soil. While APT is a well-known technique in material science, nobody had ever tried using it for lunar samples before. Studying soil from the Moon's surface gives scientists insight into an important force within our Solar System: space weathering. Space is a harsh environment, with tiny
meteorites, streams of particles coming off the Sun, and radiation in the form of solar and cosmic rays. While Earth's atmosphere protects us from space weathering, other bodies like the Moon and asteroids don't have atmospheres. As a result, the soil on the Moon's surface has undergone changes caused by space weathering, making it fundamentally different from the rock that the rest of the Moon is composed of. It's like a chocolate- dipped ice cream cone: the outer surface doesn't match what's inside. With APT, scientists can look for differences between space weathered surfaces and unexposed moon dirt in a way that no other method can. By understanding the kinds of processes that make those differences happen, they can predict more accurately what's just under the surface of moons and asteroids that are too far away to bring to Earth.
SOLAR PARTICLES FROM BEYOND EARTH FOUND NEAR SUN
Southwest Research Institute
Using data from NASA's Parker Solar Probe (PSP), a team of astronomers has identified low-energy particles lurking near the Sun that likely originated from solar wind interactions well beyond Earth orbit. PSP is venturing closer to the Sun than any previous probe. Scientists are probing the enigmatic features of the Sun to answer many questions, including how to protect space travellers and technology from the radiation associated with solar events. The main goal is to determine the acceleration mechanisms that create and transport dangerous high-energy particles from the solar
atmosphere into the solar system, including the near-Earth environment. PSP, which will travel within 4 million miles of the Sun's surface, is collecting new solar data to help scientists understand how solar events, such as coronal mass ejections, impact life on Earth. During the rising portion of the Sun's activity cycle, our star releases huge quantities of energized matter, magnetic fields and electromagnetic radiation in the form of coronal mass ejections (CMEs). This material is integrated into the solar wind, the steady stream of charged particles released from the Sun's upper atmosphere. The high-energy solar energetic particles (SEPs) present a serious radiation threat to human explorers living and working outside low-Earth orbit and to technological assets such as communications and
scientific satellites in space. The mission is making the first-ever direct measurements of both the low-energy source populations as well as the more hazardous, higher-energy particles in the near-Sun environment, where the acceleration takes place.
When the Sun's activity reaches a lull, roughly about every 11 years, solar equatorial regions emit slower solar wind streams, travelling around 1 million miles per hour, while the poles spew faster streams, travelling twice as fast at 2 million miles per hour. Stream Interaction Regions (SIRs)
are created by interactions at boundaries between the fast and slow solar wind. Fast-moving streams tend to overtake slower streams that originate westward of them on the Sun, forming turbulent corotating interaction regions (CIRs) that produce shock waves and accelerated particles, not
unlike those produced by CMEs. For the first time, astronomers observed low-energy particles from these CIRs near the orbit of Mercury. They also compared the PSP data with data from STEREO, another solar energy probe. By measuring the full range of energetic populations and correlating the data with other measurements, they hope to get a clear picture of the origin and the processes that accelerate these particles. Our next step is to integrate the data into models to understand the origin of SEPs and other materials. Parker Solar Probe will solve many puzzling scientific questions — and is guaranteed to generate new ones as well.
TITAN FAILED KEY TEST FOR LIFE
Titan, the second largest moon in our solar system after Jupiter's Ganymede, is unique in two ways that have convinced some researchers that this moon might host extraterrestrial life. It's the only moon in our solar system with a dense atmosphere, and it's the only body in space, besides Earth, known definitely to have pools of liquid on its surface. In Titan's case, those pools are frigid lakes of hydrocarbons, closer to the petrol in a car than the oceans on Earth. But some researchers have suggested that complex structures could arise in those pools: bubbles with special properties that mimic ingredients found to be necessary for life on our planet. On Earth, lipid molecules (fatty acids) can spontaneously arrange themselves into bubble-shaped membranes that form the barriers around the
cells of all known life-forms. Some researchers think this was the first necessary ingredient for life as it formed on Earth. On Titan, researchers have speculated in the past, an equivalent set of bubbles might have emerged, these consisting of nitrogen-based molecules called azotosomes. But for those structures to arise naturally, the physics has to work just right in the conditions actually present on Titan: temperatures of about minus 185 degrees Celsius), without liquid water or atmospheric oxygen.
Previous studies, using molecular dynamics simulations — a technique often used to examine the chemistry of life — suggested that such bubble structures would arise and become common on a world like Titan. But new research suggests that those earlier simulations were wrong. Using more complex simulations involving quantum mechanics, the researchers studied the structures in terms of their “thermodynamic viability”. Here's what that means: Put a ball at the top of a hill, and it's likely to end up at the bottom, a position of lower energy. Similarly, chemicals tend to arrange themseIves in the simplest, lowest-energy pattern. The researchers wanted to know whether the azotosomes would be the simplest, most efficient arrangement for those nitrogen-bearing molecules. Titan represents a
“strict test case for the limits of life”, the researchers wrote in their paper. And in that role, the moon fails. Azotosomes, the simulation showed, just aren't thermodynamically viable on Titan. This work, the researchers said in a statement, should help NASA figure out what experiments to include on its Dragonfly mission to Titan, planned for the 2030s. It's still theoretically possible that life emerged on Titan, the researchers said in the paper, but such life would probably not involve anything we'd recognize as a cell membrane.
PLUTO'S ICY HEART MAKES WINDS BLOW
A “beating heart” of frozen nitrogen controls Pluto's winds and may give rise to features on its surface, according to a new study. Pluto's famous heart-shaped structure, named Tombaugh Regio, quickly became famous after NASA's New Horizons mission captured footage of the dwarf planet in 2015 and
revealed it isn't the barren world scientists thought it was. Now, new research shows Pluto's renowned nitrogen heart rules its atmospheric circulation. Uncovering how Pluto's atmosphere behaves provides scientists with another place to compare to our own planet. Such findings can pinpoint both similar and distinctive features between Earth and a dwarf planet billions of miles away. Nitrogen comprises most of Pluto's thin atmosphere, along with small amounts of carbon monoxide and the greenhouse gas methane. Frozen nitrogen also covers part of Pluto's surface in the shape of a heart. During the day, a thin layer of this nitrogen ice warms and turns into vapour. At night, the vapour condenses and once again forms ice. Each sequence is like a heartbeat, pumping nitrogen winds around the dwarf
planet. New research suggests this cycle pushes Pluto's atmosphere to circulate in the opposite direction of its spin — a unique phenomenon called retro-rotation. As air whips close to the surface, it transports heat, grains of ice and haze particles to create dark wind streaks and plains across the north and northwestern regions.
Most of Pluto's nitrogen ice is confined to Tombaugh Regio. Its left lobe is a 1,000-kilometre ice sheet located in a 3-kilometre-deep basin named Sputnik Planitia — an area that holds most of the dwarf planet's nitrogen ice because of its low elevation. The heart's right 'lobe' is comprised of highlands and nitrogen-rich glaciers that extend into the basin. Before New Horizons, everyone thought Pluto was going to be completely flat, almost no diversity. But it is completely different. It has a lot of different
landscapes and we are trying to understand what's going on there. Astronomers set out to determine how circulating air — which is 100,000 times thinner than that of the Earth's — might shape features on the surface. The team pulled data from New Horizons' 2015 flyby to depict Pluto's topography and its blankets of nitrogen ice. They then simulated the nitrogen cycle with a weather-forecast model and assessed how winds blew across the surface. The group discovered Pluto's winds above 4 kilometres
blow to the west — the opposite direction from the dwarf planet's easterly spin — in a retro-rotation during most of its year. As nitrogen within Tombaugh Regio vaporizes in the north and becomes ice in the south, its movement triggers westward winds, according to the new study. No other place in the solar system has such an atmosphere, except perhaps Neptune's moon Triton. The researchers also found a strong current of fast-moving, near-surface air along the western boundary of the Sputnik Planitia basin. The airflow is like wind patterns on Earth, such as the Kuroshio along the
eastern edge of Asia. Atmospheric nitrogen condensing into ice drives this wind pattern, according to the new findings. Sputnik Planitia's high cliffs trap the cold air inside the basin, where it circulates and becomes stronger as it passes through the western region. These wind patterns stemming from Pluto's nitrogen heart may explain why it hosts dark plains and wind streaks to the west of Sputnik Planitia. Winds could transport heat — which would warm the surface — or could erode and darken the ice
by transporting and depositing haze particles. If winds on the dwarf planet swirled in a different direction, its landscapes might look completely different. The new findings allow researchers to explore an exotic world's atmosphere and compare what they discover with what they know about the Earth.
SPACECRAFT ALTERS THEORY OF PLANET FORMATION
Scientists say they have “decisively” overturned the prevailing theory for how planets in our Solar System formed. The established view is that material violently crashed together to form ever larger clumps until they became worlds. New results suggest the process was less catastrophic – with
matter gently clumping together instead. The claim arises from detailed study of an object in the outer reaches of the Solar System. Named Arrokoth, the object is more than six billion km from the Sun in a region called the Kuiper belt. It is a pristine remnant of planet formation in action as the Solar System emerged 4.6 billion years ago, with two bodies combining to form a larger one. Scientists obtained high-resolution pictures of Arrokoth when Nasa's New Horizons spacecraft flew close to it just over a year
ago. It gave scientists their first opportunity to test which of the two competing theories was correct: did the two components crash together or was there gentle contact? The analysis could find no evidence of violent impact. The researchers found no stress fractures, nor was there any
flattening, indicating that the objects were squashed together gently. These so-called Kuiper belt objects have largely remained the same since the formation of the Solar System. They are, in effect, perfectly preserved fossils from this distant time. When Arrokoth was discovered six years ago, it was known only by its designation 2014 MU69. At the time of the New Horizons flyby, it had been given the informal name Ultima Thule. While that name came from a classical and medieval term for a far-off place at the borders of the known world, its use by Nazi occultists as the mythical homeland of the Aryan race caused controversy. The official name Arrokoth is a Native American term meaning “sky” in the Powhatan/Algonquian language.
THE CONTINUING MYSTERY OF BETELGEUSE
For months, astronomers have been keeping a wary eye on Betelgeuse, the bright red star in Orion's shoulder. What's attracting their attention? All of a sudden, Betelgeuse isn't so bright anymore. Its luminosity has “fallen off a cliff”–a sign that the star could be on the verge of going supernova.
The most recent measurements put the visual magnitude of Betelgeuse at about +1.66, the dimmest it's been in our 25 years of photometry. Betelgeuse is a highly evolved red supergiant — the type of star that could collapse and explode at any moment. Indeed, the dimming of Betelgeuse could be explained
if the star has suddenly contracted to about 92% of its previous radius. But that's not the only possibility. Betelgeuse might be dimmed by a giant starspot — or maybe it is shrouded by an outburst of stardust from its own cool outer layers — or something else entirely. No one knows. Answers might be forthcoming on Feb. 21st. Astronomers have long known that Betelgeuse is a variable star. It pulsates with many periods. The Fourier analysis of Betelgeuse's light curve shows a dominant (probable pulsation) period of P = 430 days. Given this result, “the minimum brightness is expected on 21 (+/-7d) February 2020. If Betelgeuse starts to bounce back on Feb. 21st, this whole episode might just be a deeper-than-average pulsation, and perhaps the supernova watch can be called off. However, even
if the 430-day period is still working, this would indicate a minimum brightness near 0.9 mag — much brighter than the current value near 1.6 mag. So something very unusual is going on.
Betelgeuse isn't just dimming, it's also changing shape. The European Southern Observatory has released new images of Betelgeuse from the Very Large Telescope (VLT) in Chile's Atacama desert which reveal the unstable red supergiant is definitely lopsided. They were able to compare it to a
“normal” picture of Betelgeuse taken 11 months earlier. The change in shape is striking. The researchers aren't sure why Betelgeuse looks so different, but they suspect the involvement of dust. Red supergiants like Betelgeuse create and eject vast amounts of dusty material, losing mass even before they explode as supernovae. The lopsided shape and dimming of Betelgeuse might be explained if a cloud of dust is partially blocking its disk. Indeed, VLT infrared observations of Betelgeuse at the same time reveal lots of dust around the star. Our knowledge of red supergiants remains incomplete, and this is still a work in progress, so a surprise can still happen. Other possibilities include magnetic activity on Betelgeuse's surface (such as a giant starspot) and, of course, the early stages of a
supernova explosion. The Very Large Telescope with its adaptive optics instruments is one of the few facilities in the world capable of imaging the surface of Betelgeuse, located more than 600 light years away.
RADIO BURST REPEATS IN 16-DAY CYCLE
One of the defining characteristics of the deep-space signals we call fast radio bursts is that they are unpredictable. They belch out across the cosmos without rhyme or reason, with no discernible pattern, making them incredibly hard to study. Now, for the first time, astronomers have found a fast radio burst (FRB) that repeats on a regular cycle. Every 16.35 days, the signal named FRB 180916.J0158+65 follows a similar pattern. For four days, it will spit out a burst or two every hour. Then it falls silent for
12 days. Then the whole thing repeats. Astronomers with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Collaboration in Canada observed this cycle for a total of 409 days. We don't yet know what it means; but it could be another piece in the complicated conundrum of FRBs. It's easy to become somewhat obsessed with fast radio bursts, a fascinating space mystery that has so far defied any attempts at a comprehensive explanation. FRBs are hugely energetic flares of radiation in the radio spectrum that last just a few milliseconds at most. In that timeframe, they can discharge as much power as hundreds of millions of Suns. Most of them spark once, and we have never detected them again. This makes it difficult to track these bursts down to a source galaxy. Some FRBs spit out repeating radio flares, but wildly unpredictably. These are easier to track to a galaxy, but so far, that hasn't brought us a great deal closer to an explanation.
Last year, the CHIME collaboration announced they had detected a whopping eight new repeating fast radio bursts, bringing the then-total of repeaters to 10 out of over 150 FRB sources. FRB 180916.J0158+65 was among the eight repeaters included in last year's haul; apart from its repeat bursts, initially it didn't appear to be anything special. But as the CHIME experiment continued to stare at the sky, a pattern emerged. This is exciting, because it offers new information that can be used to try and model what could be causing FRB 180916.J0158+65. Other objects that demonstrate periodicity tend to be binary systems — stars and black holes. The 16.35-day period could be the orbital period, with the FRB object only facing Earth during a certain part of the orbit. FRB 180916.J0158+65 is
one of the handful of FRBs that have been traced back to a galaxy. It's on the outskirts of a spiral galaxy 500 million light-years away, in a star-forming region. This means a supermassive black hole is unlikely, but a stellar-mass black hole is possible. Alternatively, winds from the companion object, or tidal disruptions from a black hole, may periodically somehow block the FRB radiation. It also can't be ruled out that the FRB source is a single, lone object such as a magnetar or X-ray pulsar, although
the researchers note that that explanation is a little harder to reconcile with the data. That's because those objects have a wobbling rotation that produces periodicity, and none is known to wobble that slowly. And radio pulsars that do have periodic intervals of several days are orders of magnitude fainter than FRBs.
UNUSUAL MONSTER GALAXY IN EARLY UNIVERSE
University of California – Riverside
Astronomers have found an unusual monster galaxy that existed about 12 billion years ago, when the Universe was only 1.8 billion years old. Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear. Even before the Universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultramassive galaxy. More remarkably, XMM-2599 formed most of its stars in a huge frenzy when the Universe was less than 1 billion years old, and then became inactive by the time the Universe was
only 1.8 billion years old. The team used spectroscopic observations from the W. M. Keck Observatory's Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance. In that epoch, very few galaxies had
stopped forming stars, and none is as massive as XMM-2599. The mere existence of ultramassive galaxies like XMM-2599 proves quite a challenge to numerical models. Even though such massive galaxies are incredibly rare at that epoch, the models do predict them. The predicted galaxies, however, are expected to be actively forming stars. What makes XMM-2599 so interesting, unusual, and surprising is that it is no longer forming stars, perhaps because it stopped getting fuel or its black hole began to turn on. The results call for changes in how models turn off star formation in early
The research team found XMM-2599 formed more than 1,000 solar masses a year in stars at its peak of activity — an extremely high rate of star formation. In contrast, the Milky Way forms about one new star a year. XMM-2599 may be a descendant of a population of highly star-forming dusty galaxies in the very early Universe that new infrared telescopes have recently discovered. The evolutionary pathway of XMM-2599 is unclear. Astronomers have caught XMM-2599 in its inactive phase and do not know what it will turn into by the present day. They know it cannot lose mass. An interesting question is what happens around it. As time goes by, could it gravitationally attract nearby star-forming galaxies and become a bright city of galaxies? The team said this outcome is a strong possibility.
Perhaps during the following 11.7 billion years of cosmic history, XMM-2599 will become the central member of one of the brightest and most massive clusters of galaxies in the local Universe. Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these
two outcomes. The team has been awarded more time at the Keck Observatory to follow up on unanswered questions prompted by XMM-2599.
Bulletin compiled by Clive Down
(c) 2020 The Society for Popular Astronomy
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