Astronomy and space news summarized by Don Lynn from NASA and other sources

OSIRIS-REx is the space probe that flew by the small near-Earth asteroid Bennu on October 20 and collected a sample of its surface material. When its controllers in mission control took images of the sample mechanism, they found that the sampling had been overly successful. It had grabbed so much soil and rock in its collection mechanism that the Mylar flap that was to contain the sample had lodged on rocks and failed to close and its precious sample was slowly escaping away into space. Controllers immediately commanded the probe to stow the sample in the sealed container designed to protect the sample on its way back to Earth. The original plan had been to conduct further tests, including a spin test that would weigh the sample, before stowing it. Arrival back at Earth is scheduled for September 24, 2023.

Asteroid Density – Scientists at the University of Colorado Boulder analyzed the tracking data of OSIRIS-REx and combined that with observations of trajectories of particles thrown off by asteroid Bennu, giving them a map of the asteroid’s gravity field. Bennu was known to be essentially a pile of rubble, filled with void spaces between its constituent rocks held together by gravity. The gravity map surprisingly showed its core to be less densely packed than nearer the surface. Bennu’s spin may be pushing material outward to cause this. If so, then eventually the asteroid may spin itself to pieces.

Different Kilonova – On May 22, a short gamma-ray burst was observed by researchers at Northwestern University. Immediate follow-up observations were made in visible light, X-rays, infrared and radio. All the evidence points to a merger of two neutron stars creating a “kilonova” burst of light. A kilonova is about 1,000 times as bright as an ordinary nova, and had been observed after similar events in 2013 and 2017. This time, instead of a black hole, the new event appears to have left behind a magnetar, a neutron star with extremely strong magnetic field. The kilonova was also about ten times as bright in infrared as the previous ones meaning there seems to be at least two ways to make a kilonova. Previously magnetars were believed to be created by the explosion of massive stars at the ends of their lives, so it likewise seems to mean there are at least two ways to make a magnetar. Astronomers believe that within a few years, ejected material will start emitting radio waves, so they will continue to monitor the object.

Gravitational Waves – The scientists of the LIGO and Virgo gravitational wave detectors have released a new catalog of all of their detected wave events. It contains 50 events, including 39 that have been analyzed so far from the current observational run. Most of the events were mergers of black holes. The large increase in detected events since the first two observing runs reflects the increased sensitivity of the instrument after it was upgraded between runs. These upgrades include increasing laser power, improving mirrors, and use of quantum squeezing. The last of these is a technique to reduce the Heisenberg uncertainty in measuring the length of the wave detector arms by increasing the uncertainty in a related quantity. More upgrades will be made before the next observing run, scheduled to begin in mid-2022. The Japanese KAGRA gravitational wave detector will go into operation for that next observing run.

Brown Dwarf Discovered By Radio – Brown dwarf stars are just massive enough to begin nuclear fusion of heavy hydrogen, but not massive enough to fuse ordinary hydrogen like main sequence stars do. Although some brown dwarfs have been seen in radio light, none has been discovered by radio, until now. Observations by astronomers at the University of Colorado using LOFAR, a low frequency radiotelescope array scattered across Europe, found the radio signal emitted by a previously unknown brown dwarf. The radio waves were emitted by aurora on the brown dwarf. Most brown dwarfs have been found by infrared telescopes because their temperatures produce infrared light, but the coolest brown dwarfs are difficult to discover, as they give off very little infrared.

Extreme Weather – An exoplanet dubbed K2-141b has been discovered by scientists from McGill University, York University and the Indian Institute of Science Education, where the extreme temperature on the planet’s surface causes rock to melt into lava oceans and even evaporate into rock vapor. Winds in excess of 3,100 mph then blow the vapor to the cold part of the planet, where it rains lava and drops rock snowflakes. The planet orbits extremely close to its star and keeps one side always toward that star, resulting in temperatures over 5,400 degrees Fahrenheit on the star-facing side and as low as minus 328 degrees Fahrenheit on the unheated dark side. This surely is a candidate for the worst weather in the Universe.

Active Red Dwarf – About three quarters of the stars in our galaxy are tiny dim red dwarves. Naturally many of the exoplanets being discovered orbit this common type of star. In the search for habitable planets, astronomers have been disappointed that young red dwarf stars usually emit too much X-ray radiation and flares to allow any of their planets to be habitable, but older red dwarfs tend toward less dangerous emissions. However, recent studies by astronomers at the Netherlands Institute for Radio Astronomy of the red dwarf Barnard’s Star only six light-years away, found that it is quite active though old, showing ultraviolet and X-ray emissions and stellar flares about 25 percent of the time. So not all red dwarfs calm down in their old age.

Jovian Sprites – The Juno space probe has imaged in ultraviolet Jupiter’s equivalent of “sprites” or “elves,” forms of lightning that occur very high in the atmosphere above ordinary lightning storms. On Earth these are produced by excited nitrogen molecules and are seen in visible wavelengths of light, but on Jupiter, hydrogen molecules produce them in ultraviolet. Further observation will be attempted with Juno’s radio and plasma wave instruments. Unfortunately, the layout of Juno prevents simultaneous visible and ultraviolet observations, so it can’t be determined if visible lightning accompanies the ultraviolet phenomena.

Early Mars Water – An analysis by scientists at the University of Copenhagen and the University of Tokyo of a meteorite that came from Mars has been shown to include minerals that likely formed in water. The object was splashed off the red planet by an impact 4.4 billion years ago, indicating that bodies of water likely existed on Mars at that time, earlier than other evidence of bodies of water on Mars. The meteorite is named NWA 7533 since it was found in North West Africa, a few years ago.

Phosphine Second Opinion – In October, an international team of astronomers led by researchers from Cardiff University reported that the chemical phosphine had been found in Venus’s atmosphere. How the phosphine formed there is a mystery, because that chemical found on Earth is made by living beings. Another group of astronomers from Leiden University in the Netherlands has now analyzed the data on which the phosphine discovery was based, using different methods, and concluded that it is quite possibly noise in the data rather than the presence of phosphine. More observations are needed to settle this, possibly from future spacecraft at Venus.

Comet Surface – Six years ago the European Space Agency’s Rosetta spacecraft dropped its lander named Philae onto the surface of Comet 67P/Churyumov-Gerasimenko. Its anchor failed to hold and the lander bounced twice then wedged, taking hours between bounces in the extremely low gravity of the comet. Scientists at the ESA have now located the bounce marks and have studied them. The thin surface coating was scraped off to reveal clean water ice underneath that is fluffier than new-fallen Earth snow. It is nearly 80 percent empty space between ice particles.

Milky Way Shells – Astronomers from the Rensselaer Polytechnic Institute found a stack of shell-like structures of stars in our Milky Way galaxy. Similar structures have occasionally been found in other galaxies, but these are the first seen in the Milky Way. They were found using data from the Sloan Digital Sky Survey and Gaia space telescope. Scientists believe that these structures were formed from stars gravitationally ripped out of a dwarf galaxy that collided with the Milky Way nearly three billion years ago. A collision and subsequent oscillation that aimed nearly straight through the center of our galaxy would produce structures of this shape.

Milky Way Filaments – A team of astronomers at the Max Planck Institute of Astronomy has found a network of hydrogen filaments throughout the Milky Way. The work was the most detailed view of hydrogen yet made of the inner galaxy. The observations were made with the Jansky Very Large Array of radiotelescopes in New Mexico. Most of the filaments are parallel to the disk of the galaxy. One filament is 3,000 light-years long. However perpendicular filaments were also found, which are believed to have been created where high rates of star formation blew material out of the galactic plane.

Collisions With the Milky Way – Astronomers at the University of Heidelberg analyzed the spectra of the approximately 150 globular clusters that orbit our galaxy, as well as the shape and orientation of their orbits. They determined that five subgroups of globulars were captured from satellite dwarf galaxies when they collided with the Milky Way. The dates of collisions and numbers of captured globulars are:

It is possible that many other collisions took place but did not contribute captured globulars. Computer simulations of collisions with a model of the Milky Way were used to derive the dates. The five collisions resulted in our galaxy capturing about a billion stars, a tiny fraction of those now in the Milky Way.

Bulge Star Ages – Previous studies of the stars in the central bulge of the Milky Way galaxy showed that they fell in at least two general age groups, implying that the center of the galaxy underwent two or more bursts of star formation in its history. However, a new study by researchers at the Space Telescope Science Institute and UCLA, of millions of stars in the central bulge, concluded that it had only one burst of star formation that occurred more than 10 billion years ago. The ages of the bulge stars have traditionally been determined by spectroscopically measuring the concentrations of elements heavier than helium. The new study concluded that the heavy elements built up much more quickly in the bulge than other galactic areas, so all of the bulge stars with various heavy element content were quite old. More studies are planned of bulge stars, studies that include distance measurements and orbital motion measurements of the stars.

Ring Finally Explained – A mysterious ring about a star, seen in ultraviolet light by the GALEX space telescope, has finally been explained after 16 years of study by astronomers at Caltech. About 2,000 years ago, a much smaller star collided with the star, named TYC 2597-735-1. The two stars merged and threw out a cloud of debris. A disk of gas cut the debris into two cones moving in opposite directions and which glow in ultraviolet. The initial GALEX images had been interpreted as the result of a supernova, but follow-up observations in infrared and visible light kept turning up features that didn’t fit the supernova theory.

Water On the Moon – Several discoveries of water ice on our Moon in shadowed areas within craters have been announced in recent years. Now, new observations by researchers at the University of Hawaii at Mānoa, made with SOFIA, an airborne 100-inch infrared telescope, have found water ice in some sunny areas of the Moon. The ice is mixed in the surface soil in concentrations of about 100-400 parts per million. Previous observations of sunny areas of the Moon have found evidence that could be of either water or hydroxyl, but the new observations are definitely water. These observations are the first time SOFIA has looked at the Moon, because it was designed to track on stars, not the Moon. Because conditions in sunny areas of the Moon should eventually drive water off into space, there must be a means of replenishing the water. Further observations of other areas of the Moon at different sunlight angles are planned.

Moonlike Asteroid – There are thousands of asteroids orbiting the Sun in Jupiter’s orbit, at a roughly 60 degree angle ahead or behind the giant planet. These locations are two of the gravitationally stable Lagrange zones, formed by the combined gravity of the Sun and Jupiter. The objects are known as Trojan asteroids because the first ones discovered happened to have been named after various heroes of the ancient war between Troy and Greece. In recent years Trojans have been found in smaller numbers in the orbits of many of the other planets, including Mars. A new study by astronomers at Armagh Observatory of a Martian Trojan, asteroid 101429, found spectroscopically that its surface material is quite similar to that of Earth’s Moon. An obvious theory would be that the impact of a large object with Earth that formed our Moon more than 4 billion years ago also threw material out to Mars’s orbit. Other explanations of the asteroid’s surface composition have also been proposed, so more work is needed before being certain that this Martian Trojan is a wayward piece of Earth.

Earth’s Magnetic Reversal – Every few hundred thousand years, at somewhat irregular intervals, the Earth’s magnetic field reverses itself, and the north and south magnetic poles swap. This is known by measuring the magnetic fields in rocks that formed at different times in Earth’s history. New research, led by researchers at the National Institute of Polar Research in Japan, of a rock record in central Japan has revealed details of the last time a reversal occurred, about 773,000 years ago. They found that the Earth’s magnetic field had been going through an unstable period for at least 10,000 years before the reversal and the reversal process took at least 20,000 years. This contradicts some previous studies that concluded that reversal was much quicker.

Space Station – Humans have been living on the International Space Station continuously for 20 years, as of November 2. More than 240 people from 19 countries have stayed there. The second ever SpaceX Falcon rocket with people aboard arrived with four more astronauts on November 16. Before the Falcon, the crews arrived on 63 Russian Soyuz rockets and 37 Space Shuttle flights. The plan is to keep seven people aboard the station for the foreseeable future, an expansion from the six that comprised a typical crew for several years past.

Voyager 2 Is Fine – NASA’s Deep Space Network (DSN) is designed so that it can communicate by radio with any distant spacecraft from at least one of its three radio dish locations at any time, as the Earth turns. An exception to this is that spacecraft located very far south can only use the Australian location. Voyager 2 is very far south, and additionally is so distant that only the largest and most sensitive DSN radio dish can be used. Since February, the 230-foot Australian dish has been undergoing repairs and upgrades, so Voyager 2 was instructed to ignore the fact that Earth wasn’t going to talk to her for months. In late October, as dish repairs neared completion, the Australian large dish checked in with Voyager 2 and found that everything aboard the spacecraft was fine.

More Bad Arecibo News – Puerto Rico’s Arecibo radio telescope has collapsed. On November 7, a second cable that supported the receiving equipment suspended high above the radio dish, snapped and further damaged the dish surface. The observatory operators had initiated a plan to repair damage from the first cable break three months previously. But after the second break, the National Science Foundation (NSF), which funds Arecibo, hired experts to assess how to repair the telescope, and their conclusion was that it could not be done without life-threatening risks to repair personnel. As a result, the NSF decided the only option left is to perform a controlled demolition of at least the suspended parts, abandoning hope of the telescope’s future use. At about 1,0000 feet across, Arecibo is the second largest radiotelescope dish in the world with a long history of important astronomical discoveries. Archived observations will remain available, and the visitor center and some auxiliary facilities will reopen after the demolition. However, before the Arecibo demolition plan was completed, and before any such work was begun, on December 1 a further failure occurred in the system supporting the receiving apparatus more than 400 feet above the dish. The entire 900 tons of suspended equipment swung down, still attached to some support cables, and smashed into the dish. The tops of the reinforced concrete support towers snapped off. Personnel were present in the control room overlooking the dish, but there were no injuries.