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

Betelgeuse – As reported here over the last two months, the star Betelgeuse dimmed to its lowest recorded level in early February. New observations made in late February showed it creeping back up in brightness. Despite much speculation about a potential supernova, the dimming does not seem to indicate an imminent explosion. Recent observations made by astronomers at the University of Minnesota in infrared wavelengths showed essentially no change in brightness from observations made years ago. This implies the dimming in visible light was caused by dust that does not block infrared passing in front of the star. Such red supergiant stars are known to occasionally throw off material that cools into dust. Also, the surface temperature was measured by astronomers at the University of Washington and Lowell Observatory, and it is too warm to cause the dimming.

Repeating FRBs – Many fast radio bursts (FRBs) occur only once. But some of them repeat from the same location. It is not clear if repeaters and non-repeaters are caused by the same phenomena, or even what those phenomena may be. In order to learn more, the McGill University team operating the CHIME radiotelescope in British Columbia, Canada has been searching for new FRBs. They announced discovery of nine new repeaters, bringing the total to twenty. Bursts from repeaters tend to last slightly longer (though still on the order of milliseconds) and show lower magnetization, supporting the theory that repeaters differ in cause from non-repeaters. Yet dispersion appears to be the same for repeaters and non-repeaters. Dispersion is caused by the interstellar matter the burst passes through on the way to us.

Neutron Star Size – Researchers led by astronomers at the Max Planck Institute for Gravitational Physics who analyzed the gravitational waves emitted by an August 2017 neutron star collision announced the most precise size for neutron stars. Their work pinned down the diameter of a typical neutron star to be between 12.9 and 14.8 miles. This is a little smaller than previous generally accepted estimates and might mean there is exotic material at the core. It is not known if neutron stars are made of pure neutrons all the way down to the core (except the very surface where pressure is not enough to be pure neutrons), or whether even more exotic material exists at the core, such as quark soup. This uncertainty has led to disagreement over how large neutron stars might be. Scientists hope to observe some collisions between black holes and neutron stars to shed more light on the interiors of neutron stars. Whether a black hole strips apart neutron stars or swallows them whole depends on the size and density of neutron stars.

Omega Centauri Pulsars Discovered – Pulsars are neutron stars that give off radio pulses or other forms of light each time they rotate. Many globular clusters have known pulsars in them and are used to determine pulsar motions within those clusters. However no pulsars had been found up to now in the largest local globular cluster, Omega Centauri. A new search by astronomers at CSIRO’s Australia Telescope National Facility using the Parkes radiotelescope discovered five pulsars in Omega, all millisecond pulsars, meaning that every rotation takes only a few milliseconds. One of them is a binary star, paired with a low-mass star that orbits it every 2.1 hours.

Protostar Study – Scientists from the National Radio Astronomy Observatory used the ALMA and the VLA radiotelescope arrays to image more than 300 planet-forming disks around young protostars in Orion. The radio wavelengths they were observing penetrate the dust and gas found around such young stars. The study yielded the average size and mass of these protostars which the researchers then compared to previous observations of older planet-forming disks. The younger disks were similar in size to older ones, but more massive, meaning that a star steals material from its disk as the star grows. This implies a planet that forms very early in the life of the disk would have more material to form the planet. Four of the protostars looked peculiarly irregular, leading astronomers to think that these four were extremely young and the protostars had not fully pulled together yet. The images also showed outflows from the protostars forming. Theoretically such outflows should dissipate spin and allow the protostars to continue growing.

Huge Flare – A very small red dwarf star, barely massive enough to not be a brown dwarf, was spotted by a team led by astronomers at the Istituto di Astrofisica Spaziale e Fisica Cosmica in Milan in archived XMM-Newton X-ray space telescope data emitting a huge flare in X-rays. It gave off more than 10 times the energy of any flare ever seen on our Sun. Astronomers haven’t been able to figure out how a star of this small mass could generate so much energy. It might be that this star flares far less frequently than most stars, building up lots of energy before releasing it. More study is needed of this or similar stars.

Eclipsing Brown Dwarfs – While an international team of researchers on a project called SPECULOOS were testing a new 1-meter telescope in Chile by focusing on a known brown dwarf star, they were surprised to find it dimmed for 90 minutes, indicating something passed in front of it. Brown dwarfs are stars without quite enough mass to sustain nuclear fusion, the process that powers ordinary stars. Further observations using larger telescopes showed that two closely orbiting brown dwarfs were eclipsing each other. Eclipsing brown dwarfs are rare, this being the second such pair known. They are valuable to astronomers because they can calculate the masses, orbital distance, and sizes of the pair. In this case, the age of the brown dwarfs is also known because they belong to a star cluster whose age had previously been determined. Additionally there is a third brown dwarf distantly orbiting the newly found pair. Triple brown dwarfs are also rare.

Largest Known Explosion – Astronomers at the Naval Research Laboratory in Washington, DC, discovered a huge cavity in the center of the Ophiuchus galaxy cluster and believe that it could only have been caused by a huge explosion centered on a massive galaxy in the cluster. To make a cavity this large, it would have been the largest explosion known. That much energy could have only come from record-breaking activity at the supermassive black hole in the center of this massive galaxy. The edge of the cavity was first detected using X-ray data and was confirmed using radiotelescopes. Astronomers were unable to find jets at the black hole, so apparently the black hole activity that caused the cavity has subsided. This galaxy cluster is 390 million light-years away.

Sombrero Galaxy Study – A new study by astronomers at the Space Telescope Science Institute of data taken by the Hubble Space Telescope of the Sombrero Galaxy’s halo showed that it is mostly composed of metal-rich stars. This is surprising because most galaxy halos are chiefly metal-poor stars. Metal-poor stars form from pristine gas, usually early in the history of a galaxy. As a galaxy ages, heavy elements, including metals, build up from nuclear fusion in stars and from supernovas. Then those elements are dispersed all over the galaxy’s disk and bulge by stellar winds and supernovas, but not usually all the way out to the halo. Stars that form later in the disk or bulge will be metal-rich stars. Likely these late generation stars were dispersed into the halo of the Sombrero by some process that doesn’t occur often in other galaxies, possibly a collision with a major galaxy. Collision with small galaxies won’t account for the metal-poor stars, and are common. However, a collision with a major galaxy usually destroys the shape of the galaxy’s disk, which did not happen with the Sombrero. Possibly the halo is simply short of metal-poor rather than long on metal-rich stars. This would imply that the normal dissipation of metal-poor stars from globular clusters into the halo didn’t happen in the Sombrero, but more work is needed to fully explain this unusual galaxy.

Iron Rain – Observations by astronomers at the University of Geneva of an exoplanet known as WASP-76b with the Very Large Telescope in Chile show that it rains molten iron there. The daytime temperature there was measured at 4,300 degrees Fahrenheit, caused by its close orbit around its star. This is hot enough to vaporize iron, and indeed iron vapor has been found in spectra of the planet. High winds blow the vapor over to the night side, where it is a relatively chilly 2,700 degrees Fahrenheit, causing the iron vapor to condense and rain down as molten iron. Take a tungsten umbrella if you visit this planet. It is 640 light-years away in the constellation Pisces.

Exoplanet Found By Aurora – Astronomers have found a new way to detect exoplanets. Led by researchers at the Netherlands Institute for Radio Astronomy, they spotted a probable exoplanet orbiting the red dwarf star GJ 1151 by detecting its aurora with the radiotelescope array LOFAR in the Netherlands. The aurora there is caused by a magnetic connection from the star to planet, similar to auroras on Jupiter caused by magnetic connection to Io’s volcanoes. This is different from auroras on Earth that receive their particles from the solar wind, not a magnetic connection. Astronomers plan to confirm this planet, and look for others with detectable aurora. Such planets should be common because red dwarf stars are the most common type and usually have strong magnetic fields.

Lunar Regolith – Scientists at the Chinese Academy of Sciences analyzed the data from the ground-penetrating radar on board the Chinese lunar rover Yutu-2 and found three layers of differing composition in the lunar soil, known as regolith. Soil from the surface down to 39 feet is fine material with some larger rocks. The regolith from 39 to 79 feet has increasingly large rocks, and depth below this has alternating fine and coarse material. Good data was received from as deep as 121 feet. The radar has two frequencies, 60 and 500 MHz, and only data from the higher frequency has been analyzed. When scientists analyze the other frequency, they expect data from much deeper. Yutu-2 is part of the Chinese Chang’e 4 mission that landed on the Moon’s far side last year.  Yutu-2’s predecessor’s radar was able to penetrate only 33 feet in depth, due to different material found at its landing site. Lunar regolith is the result of billions of years of meteoroid impacts breaking up and churning the once rocky surface. All instruments aboard Yutu-2 and its lander are working perfectly more than 14 months after landing.

Another Moon – In February astronomers at the Catalina Sky Survey discovered an asteroid orbiting Earth. Known as 2020 CD3, it is about the size of a car and takes 47 days to complete each trip around us. Tracing its path back, it likely was captured by Earth about three years ago and tracing forward it is expected to escape this month. Only one other such temporary moon has ever been seen, and that was 2006 RH120. It is likely an asteroid, as no known rocket parts or spacecraft should be in the vicinity.

New TNOs Discovered – Researchers at the University of Pennsylvania used a custom-built computer program to look through archived data from the Dark Energy Survey to find objects that moved like Trans-Neptunian Objects (TNOs) and found 316 of them, including 139 new discoveries. This is a substantial addition to the only about 3,000 TNOs known. The objects found range from about 30 to 90 AU from the Sun, about 30 to 90 times the Earth’s distance from the Sun. The Dark Energy Survey was conducted using the Victor M. Blanco 4-meter telescope in Chile, which was fitted with a super wide-angle camera known as the Dark Energy Camera, one of the world’s largest astronomical cameras. Researchers saw about seven billion objects in the data, of which 22 million moved, but only 400 of these moved like a TNO. The researchers are now running their program again with a lower threshold of detectability, which should find hundreds more TNOs.

Bennu Features Named – The first names of features on asteroid Bennu have been accepted by the IAU. The theme chosen for features there is mythical birds and their places. Most of the new names are applied to rocks (“Saxa” in Latin), because they’re what make up most of the features on this tiny asteroid only about one third of a mile in diameter. These features have been discovered by the orbiting spacecraft OSIRIS-Rex.

Titan’s Atmosphere – Astronomers at  the University of Tokyo analyzed archived spectroscopic observations of Saturn’s moon Titan by the Chilean radiotelescope ALMA to determine the ratio of the chemical compound acetonitrile containing ordinary nitrogen to that containing the heavier isotope of nitrogen. The ratio matched what was theoretically predicted if the acetonitrile were produced by cosmic rays striking the atmosphere. Nitrogen ratios differed for other compounds, such as hydrogen cyanide, indicating they were produced by ultraviolet from the Sun striking the atmosphere, not cosmic rays. Ultraviolet is absorbed higher in Titan’s atmosphere than cosmic rays, so this tells us which nitrogen compounds exist at higher and lower altitudes.

InSight Progress Report – The Mars InSight team has stated that efforts to get the craft’s heat probe pounded into the Martian soil seem to be working. InSight controllers are using the craft’s arm to press on the probe while simultaneously pounding with the probe’s internal hammer. Previous efforts have failed because the soil kept rebounding the probe, negating hammering progress. It has to reach 3-5 yards under the surface to get good readings on the heat escaping from the core of Mars.

The count of marsquakes detected by InSight has now exceeded 450. Most have been fairly small, less than magnitude three. Scientists are hoping for bigger ones, because they can reveal more about the interior structure of the planet. It is believed the cause of marsquakes is cooling and shrinkage of the planet. Impacts may also contribute to marsquakes.

Martian Magnetic Fields – A research team led by astronomers at the University of British Columbia announced results from the InSight magnetic sensor shows that the magnetic field at the landing site is about ten times stronger than had been measured by orbiting spacecraft, implying that Martian magnetic fields are more localized than can be measured accurately by distant sensors. InSight data also indicated that the magnetic field varies over seconds and days. It is believed that the magnetic field is caused both by magnetic rocks underground and by events in the upper atmosphere related to disturbed solar wind. Magnetic pulses around the Martian midnight have been detected which probably result from a shift in solar wind interacting with the planet. Researchers plan to make surface magnetic measurements with InSight simultaneously with measurements from the MAVEN orbiter passing overhead.

Rover Named – NASA announced the winner of a contest to name the Mars 2020 rover. Alexander Mather, a 13-year-old middle school student submitted the winning essay, and so the rover is henceforth known as “Perseverance.” NASA received 28,000 entries, and judges narrowed the field to 155 semifinalists, and then nine finalists. The public voted on the nine to determine the winner. All 155 semifinal essays have been written on a microchip that will accompany the rover to Mars. Mather will be sent to Florida to watch the launch of Perseverance in July.

Mars Launch Delayed – The launch of ExoMars 2020 has been postponed until the next alignment of Earth and Mars, in 2022. This mission is a joint European and Russian project that includes a lander and a rover with a drill to sample soil more than six feet below the Martian surface. The testing still to be done was judged unachievable this year, particularly with the travel restrictions in Europe due to the Corona Virus. The lander has 13 instruments and the rover nine. The rover has been named Rosalind Franklin, honoring the chemist’s role in discovering the structure of DNA.