Hydrogen Filament – A group of astronomers at the Max Planck Institute for Astronomy has identified the radio signature of a giant filament of atomic hydrogen 3,900 light-years long and 130 light-years wide, located near the far side of our Milky Way galaxy. One of the discoverers has dubbed the feature Maggie, after the river Magdalena. If Maggie cools enough in the future, it could convert to molecular hydrogen and supply material for star formation. It is now much bigger than any known star-forming clouds of molecular hydrogen.
New Class of Nebula – A team of astronomers at the University of Innsbruck identified a new class of nebula. It’s found in binary star systems after one of the stars swells up as a red giant and it engulfs the other. This is already known as a common-envelope system, but if the system then ejects part of its envelope, it forms this new class of nebula. This differs from a planetary nebula because a planetary nebula does not have the companion star engulfed in the red giant. The new nebula class has not been observed before because they quickly expand to huge size, becoming quite faint, and last only a few hundred thousand years (brief in cosmic time scales). The first example was found by a group of amateur astronomers, then professionals proved that it was something new. The size of this object is over 15 light-years across. The nebula has about the mass of our Sun and was ejected about 500,000 years ago.
The Local Bubble – It has long been known that our Solar System is located in a 1,000-light-year-wide bubble with fewer stars than typical, believed to have been created by multiple supernova blasts over past millions of years. A new study by researchers at the Harvard & Smithsonian Center for Astrophysics and the Space Telescope Science Institute put together a history of this bubble. A series of about 15 supernovas exploded in this region over the past 14 million years. Interstellar gas collected along the edges of the resulting bubble, giving rise to seven star-forming regions that created all the nearby young stars. The Sun’s motion about the Milky Way galaxy caused it to enter this bubble only about 5 million years ago and has now reached a point near the center of the bubble. The study’s authors plan to use similar techniques to put together histories of other bubbles within our galaxy.
Galaxy Without Dark Matter – A few years ago astronomers announced finding that two ultra-diffuse galaxies, named NGC 1052-DF2 and DF4, were found to have essentially no dark matter. Every other galaxy whose dark matter has been measured has much more dark matter than ordinary matter, so the finding has been disputed ever since. Astronomers at the University of Groningen discovered another ultra-diffuse galaxy, designated AGC 114905, also with little or no dark matter. Dark matter levels are measured by determining the speeds of gas clouds orbiting the galaxy. Ultra-diffuse galaxies are ones roughly the size of the Milky Way, but with 1,000 times fewer stars in them.
Pre-Supernova Observations – For the first time, astronomers at the University of Hawaiʻi monitored a red supergiant star for more than four months before it exploded as a Type II supernova. Astronomers at the Pan-STARRS telescope in Hawaii spotted a great increase in brightness of a distant star. They kept watch on the star, which exploded 130 days later. Spectra taken immediately after the explosion showed that exploded material was colliding with material around the star, which was probably thrown off during the brightening 130 days earlier. The supernova was designated SN 2020tlf, and took place in the galaxy NGC 5731 about 120 million light-years away. The star was about 10 times the mass of our Sun before exploding. The few other red supergiants that have been observed before exploding were not caught undergoing a brightness surge. More observations prior to supernova explosions are needed to determine which behavior is typical.
Wolf-Rayet Supernova – Wolf-Rayet stars are massive stars nearing the ends of their lives. Due to very powerful stellar winds, they cast off a great deal of material to form a surrounding nebula rich in ionized carbon, neon and nitrogen, but lacking in hydrogen. There has been no convincing case of a Wolf-Rayet star exploding as a supernova however, leading some astronomers to propose that they don’t explode. But a new study by researchers at the Weizmann Institute found that supernova SN 2019hgp had a surrounding nebula with the ions found about Wolf-Rayet stars, indicating that at least some Wolf-Rayet stars do explode as supernovas.
Stellar Flyby – Scientists at the University of Victoria, using two radiotelescope arrays, found that a star intruded on the Z Canis Majoris binary protostar system, leaving behind a trail of dust and gas gravitationally strung out. This is probably the best observed case of a star flying through another star system. The flyby caused major impacts on the circumstellar disks that may be forming planets.
Magnetar Eruption Oscillations – A team of scientists at the Instituto de Astrofísica de Andalucía has measured oscillations in the brightness of a magnetar during its violent eruption for the first time. Magnetars are neutron stars with extremely powerful magnetic fields. About 30 of them are known. Detecting their eruptions is difficult because they last only a fraction of a second. The new eruption was seen in April 2020 by ASIM, an instrument on the International Space Station. The oscillations seen are consistent with their being produced by Alfvén waves in the magnetar’s magnetosphere. The event occurred in the Sculptor galaxy group, about 13 million light-years away, the farthest of any known magnetar eruption.
Light Weight Supermassive Black Hole – Researchers at Dartmouth College, using the Chandra X-ray space telescope, found a supermassive black hole at the center of the dwarf galaxy Markarian 462. It has one of the smallest masses of the supermassives, at about 200,000 times the Sun’s mass, which is not surprising considering Markarian 462 is a small galaxy. The study looked at eight dwarf galaxies in X-rays, that showed hints in visible light that they might contain central black holes, but Markarian 462 was the only one whose X-rays showed that material was falling into a central black hole. The black hole is heavily obscured in visible light by gas. Black holes in this “low” mass range are rarely found. Astronomers hope further study of it might show how black holes grow to the supermassive range. Searches for other low-mass supermassive black holes will continue.
Eccentric Black Hole Orbits – Scientists at the Rochester Institute of Technology studied the gravitational wave data from the merger of the two most massive black holes seen by gravitational wave detectors. They matched the recorded data to computer simulations of black hole mergers, and concluded that the merger was likely between black holes in a very elongated (eccentric) orbit about each other. This may help explain how these particular black holes came to have more mass than theory says should occur in black holes that originated with the collapse of massive stars. Black holes that form in regions dense with other black holes would be likely to devour smaller black holes, and in the process, end up with more than theoretical masses and in eccentric orbits with other black holes.
Eccentric Exoplanet – A team led by researchers at the University of Bern discovered an exoplanet orbiting a nearby red dwarf star with a highly eccentric orbit. The planet is designated TOI-2257 b and is sub-Neptune in size. It was found by its transit across its star by the TESS planet-finding space telescope. Follow-up observations showed it orbits in 35 Earth days. Its average distance from its star puts it in its habitable zone, the distance where temperatures would allow liquid water to exist on its surface. However, it is likely a gas giant without a real surface, and its eccentric orbit takes it out of the habitable temperature range for part of each orbit.
Free-Floating Planets – Astronomers at the Université de Bordeaux, using several ground- and space-based telescopes, discovered at least 70 more planets that do not orbit any star, known as free-floating planets or FFPs. They were found in a study of the Upper Scorpius OB stellar association, the nearest area of star formation to Earth. They also found about 100 more candidates that may be FFPs. The team worked hard to weed out other points of light that are not FFPs in both visible and infrared light. This study nearly doubled the total of FFPs known. FFPs are normally extremely difficult to find because they are so dim, but the ones in this OB association are quite young, less than 10 million years old, and so still glow from their original heat of formation. The astronomers involved believe that at least some of the FFPs formed while orbiting around stars but were thrown out by unstable gravitational conditions with neighboring planets. This implies that such unstable conditions can frequently arise in the first few million years of life of planetary systems. If this OB association is typical, then the Milky Way must have billions of FFPs, which are simply too dim to have been discovered.
Exoplanet Magnetic Field – A team of astronomers at the University of Arizona used data from the Hubble Space Telescope to find the first evidence of a magnetic field around an exoplanet. The analyzed ultraviolet spectra showed charged carbon particles forming a halo and tail about the exoplanet. A magnetic field best explains the shape and movement of the particle cloud. The exoplanet is known as HAT-P-11b, is 123 light-years away, and about the size of Neptune. The Earth’s magnetic field protects us from charged particles from space. Hence magnetic fields around exoplanets likely make them more conducive to harboring life. This particular exoplanet, however, is likely a gas giant like Neptune, so would not be a good place for life, even with its magnetic field.
Doomed Exoplanets – Astronomers at the American Museum of Natural History and the University of Hawai’i at Manoa have discovered three planets orbiting close to their stars and probably losing orbital distance. The closest, designated TOI-2337b, is estimated to fall into its star within a million years. All are gas giants first discovered by the TESS planet-finding space telescope then confirmed with the Keck telescope in Hawaii. Their masses are between 0.5 and 1.7 times that of Jupiter, and their diameters range from slightly smaller than Jupiter to 1.6 times that. Their densities range widely, indicating they may have formed differently. Continued observation may allow better estimates of the lifetime the three have left before falling into their respective stars.
Exomoon Candidate – In 2018 astronomers announced the discovery of an exomoon candidate, a body orbiting an exoplanet. The astronomers at Columbia University now announced another exomoon candidate, designated Kepler-1708 b-i. It is larger than any moon in our Solar System, being almost as large as Neptune. It orbits a planet the size of Jupiter, which orbits a star similar to our Sun. The system lies 5,700 light-years away. The size of the exomoon’s orbit around its planet is about the same size as Europa’s orbit around Jupiter in our Solar System. The exomoon’s parent planet’s orbit around its star is about the size of Mars’ orbit around the sun. Astronomers have not been able to move the first exomoon from candidate status to confirmed status, so the second exomoon may remain a candidate for considerable time. Future research plans include continuing to search using Kepler data for exomoons, and using the Hubble or Webb space telescopes to look for exomoons.
Another Ocean – A new study by researchers at the Southwest Research Institute analyzing old data from the Cassini Saturn orbiter showed libration in the rotation of the Saturnian moon Mimas that is best explained by a liquid ocean beneath its icy surface. Unlike Enceladus and Europa, two other moons with subsurface oceans, Mimas shows no cracks or other signs of surface geologic activity. Mimas is heavily cratered, indicating that no surface activity, other than impacts, has occurred there for billions of years. Likely, tidal flexing generates internal heat to keep the ocean liquid, but the icy shell is thick enough to prevent surface activity. Computer simulations matched observations best with an icy shell between 14 and 20 miles thick. A more precise measure of the shell thickness could be obtained by measuring the heat radiated by Mimas’ surface, an item on the wish list for a future Saturn mission.
InSight In Safe Mode – InSight, the Mars lander measuring marsquakes with its seismometer, went into safe mode when a major dust storm reduced the solar panel energy output to levels too low to maintain full operation. Spacecraft controllers later brought InSight out of safe mode, and are awaiting more output from the solar panels, as the dust storm clears, before turning on the seismometer and other instruments.
Ingenuity Flight Delayed – The same dust storm that shut down InSight also delayed the 19th flight of the Mars helicopter Ingenuity. The flight plan is to fly to the river delta that once flowed into the ancient lake in Jezero Crater, to help mission controllers plan future activities for the Perseverance rover.
Carbon Isotopes on Mars – Mars rover Curiosity measured unusually high levels of the isotope carbon 12 when analyzing the powder drilled from various surface rocks. On Earth, most concentrations of carbon 12 are caused by bacteria, but there are two other theories of its concentration that do not involve life: ultraviolet action in the atmosphere, or long-past collision with a carbon-rich giant molecular cloud. Curiosity is the first Mars mission with capability to measure carbon isotopes. Scientists are eager to get more data to try to distinguish what process caused these concentrations of carbon 12.
FRB Alerts – Scientists at McGill University developed a computerized system that notifies astronomers immediately every time a fast radio burst (FRB) is found by the CHIME radiotelescope. FRBs are powerful bursts of radio energy that last only milliseconds, and their cause or causes are not understood. Some of them repeat from the same source, but many do not. CHIME sometimes finds several FRBs in a day. The system sifts through about a million gigabytes of data every day of operation to locate FRBs. Astronomers hope that observing the sources of FRBs with other wavelengths of light will shed light on the causes of FRBs.
