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

Betelgeuse, although long known to vary somewhat in brightness, is the dimmest it’s been in at least a century. Before these recent variations, it had been brighter than Rigel at its peak, but recently dimmed to the level of Bellatrix, dimmer than first magnitude. Located in the shoulder of the constellation of Orion, Betelgeuse is a red supergiant star nearing the end of its life more than 640 lightyears away. There’s debate about whether this is just an unusual variability or the prelude for it exploding as a supernova, but few astronomers expect an explosion before 100,000 years or so. Should it explode, astronomers expect it to become one of the brightest objects in the night sky. Watch and see.

Future Star Collision – A new study by astronomers at Louisiana State University of the cataclysmic variable binary star V Sagittae shows that its two component stars are slowly moving closer to each other. Computer simulations predict that they will collide with a huge flash sometime in 2083, give or take a few years. The pair consists of a white dwarf star and a much more massive star that dumps material onto the white dwarf. Occasional fusion flares of the hydrogen in the dumped material are what make this pair vary in brightness. The pair is about 7,800 light-years away, which will make the collision spectacular to see from Earth but not dangerous. The stars now orbit each other over a period of 12 hours. Because the dumping star is more massive than those typically found in cataclysmic variable stars, V Sagittae is quite bright for this type. The mass also creates a stronger stellar wind.

OSIRIS-Rex has been orbiting the asteroid Bennu for about a year, studying it and looking for a place to land and take a sample. Four potential sites were looked at, each named for birds, and now the landing site has been chosen: Nightingale. The choice was difficult because Bennu is much rockier than expected, and there are few places safe to land between rocks. Nightingale is a relatively fresh impact crater, with exposed, fresh material that hasn’t been aged by cosmic radiation exposure for long. The landing is scheduled for August, and the return of the sample to Earth for lab analysis will be in September 2023.

New Class of Asteroid – Astronomers using the Zwicky Transient Facility found the first asteroid whose entire orbit is located within the orbit of Venus, naming it 2020 AV2. Based on its brightness, it can only be a few miles in diameter. Known as Atira asteroids, only a few dozen asteroids have ever been found with orbits inside the Earth’s. The new class inside Venus has been called Vatira asteroids. Objects inside the Earth’s orbit are difficult to find, since they always appear near the Sun when viewed from Earth. 

CHEOPS, a European satellite, was launched into Earth orbit in December. Its purpose is to study exoplanets that were discovered by other means, such as by Kepler and TESS space telescopes or ground-based telescopes. It should obtain precise sizes for exoplanets. Additionally, it could find other planets in the same systems that it is studying, and potentially even rings or moons. If ground based studies of the same planets yield masses, then the precise sizes from CHEOPS would allow astronomers to calculate densities, yielding insight into what the planet is made of. CHEOPS is planned to operate for at least three and a half years.

NEID, the extreme precision spectrometer mounted on the WIYN 3.5-meter telescope in Arizona has seen its first light. It will be used to detect the subtle wobble in stars resulting from the gravitational effects of exoplanets orbiting them. One feature that contributes to NEID’s precision is that its optics are kept at constant temperature, maintained to within one one-thousandth of a degree.

Thuban Eclipses – NASA’s Transiting Exoplanet Survey Satellite (TESS) was designed to find exoplanets as they pass in front of stars. But astronomers have been using it to discover much more. Observing an area that included the well-studied star Thuban in the constellation Draco, Angela Kochoska, a postdoc at Villanova University announced her team found that its dimmer companion star has mutual eclipses with Thuban. The star was long known to have a companion, but the eclipsing is new knowledge. The eclipses last only six hours out of the 51-day orbit. Thuban is so bright, larger telescopes rarely observe it or their sensors are saturated when they do, which likely contributed to why these eclipses have never been seen before. Mutually eclipsing stars are important because they allow astronomers to accurately calculate the sizes and masses of both. The TESS data on Thuban was studied because there had been a report that the star pulsates. However, no pulsations were found, only eclipses. About 4,700 years ago, due to the slow wobble of Earth’s axis, Thuban was near the north pole of our sky and was the North Star for a time.

Exoplanet Discoveries – New interesting discoveries were announced by the TESS team:

• A high-school summer intern at NASA unraveled the causes of TESS observations of a star that the computer analyses could not. Wolf Cukier, then at Scarsdale High School in New York and now at NASA’s Goddard Space Flight Center found that the star was an eclipsing binary star with a transiting exoplanet. The stars orbit each other every 15 days, and the planet orbits about the pair in 93-95 days (it varies depending on the positions of the stars). TESS was only sensitive enough to detect the planet transiting the larger of the stars, not the smaller. The system lies 1,300 light-years away in Pictor. The planet has been numbered TOI 1338 b. It is the first circumbinary planet (one that orbits outside a pair of stars) discovered by TESS, though about a dozen other circumbinaries are known. Many more circumbinary planets are likely to be found in TESS data. The tilt of the planet’s orbit is wobbling, so the transits will disappear from our point of view in November 2023, but will resume about 2031.
• A team at the Harvard & Smithsonian Center for Astrophysics announced the first Earth-sized planet discovered by TESS in a star’s habitable zone, the distance where the star’s heat makes the planet’s temperature suitable for liquid water. Though a few such planets have been discovered by other telescopes this is the first one found by TESS. The planet is called TOI 700 d, which is short for “TESS Object of Interest.” It is 20 percent larger in diameter than Earth and orbits its sun every 37 Earth days. It lies somewhat over 100 light-years away in Dorado, a far southern constellation. Its star is a dim red dwarf with two other planets orbiting. All three of the planets are likely tidally locked, meaning one side of them is always facing their star. On these worlds, night and day are places, not times. This could make climate and weather there far different than on Earth. In 11 months of observations, the red dwarf appeared to stay remarkably calm, with no flares seen.
• A planet in a system of three red dwarf stars was found. The star system is known as LTT 1445ABC. The planet orbits the primary of the three stars. The planet is more than 30 percent larger in diameter than Earth. It is not clear if it is a rocky planet or a subneptune gas planet. It is only about 22 light-years away, making it the second closest transiting planet known, making it a great planet for further study.

Central Milky Way Study – A team of European astronomers released a new infrared mosaic image of the center of our Milky Way galaxy, taken by the Very Large Telescope in Chile. These wavelengths of infrared penetrate the dust in our galaxy well, revealing features never seen before. Over three million stars are in the image. Findings from analyzing this image: 80 percent of the stars in this region formed early in our galaxy’s history, in the range 8 to 13.5 billion years ago; another burst of star formation occurred in this region a billion years ago, which included many very massive stars, that just millions of years later exploded as over 100,000 supernovas.

Carbon Clouds – Astronomers led by researchers at the University of Copenhagen using data gathered by ALMA, a radio telescope array in Chile, found huge clouds of gaseous carbon surrounding young galaxies. Although some stars are known to produce a lot of carbon, theory had not predicted that the carbon would spread out beyond the edges of such galaxies. The carbon was found by combining archived ALMA data observing many distant galaxies, so that astronomers are seeing them as they were when the light left them, early in the galaxies’s lives. It is believed that the carbon was spread outside the galaxies by jets or radiation from black holes or supernovas. More work is needed to explain how so much carbon spread.

Pulsars and Cosmic Rays – Astronomers at NASA’s Goddard Spaceflight Facility, using the Fermi Gamma-ray Space Telescope to study the nearby pulsar Geminga, found a faint but large halo of gamma rays. The pulsar is about 800 light-years away in the constellation Gemini. Because the halo is faint, astronomers had to first remove all known sources of gamma rays from the observations, to see the unknown sources left behind. Astrophysicists believe that the gamma ray halo is caused by high-speed electrons and positrons colliding with light photons, boosting their energies to gamma rays. The energies of gamma rays observed match this theory. The high-speed electrons and positrons near pulsars are believed to be a source of cosmic rays. This has been difficult to prove because cosmic magnetic fields bend the paths of such charged particles, so that they arrive at Earth from different directions than they would if they traveled directly from their sources. The strength of the Geminga halo indicates this could be the source of as much as 20 percent of high-energy positron cosmic rays that have been measured arriving at Earth. This supports the theory that pulsars are the major source of this type of cosmic ray.

Neutron Star Collision – The gravitational wave detector LIGO has observed its second ever collision of two neutron stars. All LIGO detections other than these two have been of colliding black holes. Unlike the first neutron star collision, this second detection has not been seen in any form of light. The calculated mass of the neutron stars was much larger than the first instance, and this may be related to why a visible explosion was not seen. There are 17 known close binary neutron stars that will likely one day collide, and the mass of this new collision is higher than the masses of those known pairs. More work is needed to determine why this collision had such a large mass. Computer simulations of the new collision indicate it may have formed a black hole.

Triggered Reconnection – NASA’s Solar Dynamics Observatory (SDO) observed a magnetic explosion in the Sun’s atmosphere unlike any seen before. Known as a magnetic reconnection, magnetic field lines in the Sun’s atmosphere often get twisted and break, reforming in a new configuration. This SDO observation was the first reconnection observed to be triggered by another event, in this case a prominence, a large loop of material ejected from the surface. The prominence was hotter after the reconnection, indicating that the reconnection added heat energy to the prominence.

Early Galaxies – A study led by astronomers at the Max Planck Institute for Astronomy using the Very Large Telescope in Chile looked at 31 distant quasars, so far off that light left there 12.5 billion years ago. Astronomers are seeing these quasars as they were very early in their lives. Twelve of them were found to be surrounded by huge halos of cool dense gas. These halos contained enough material to both form large numbers of new stars and feed the central black holes, which produces the prodigious light of the quasars. This is more gas, by billions of solar masses, than previous observations of early galaxies have found. The study is one step towards explaining how early galaxies developed huge populations of stars and huge central black holes.

Off Center Black Holes – A new study led by astronomers at Montana State University using the Jansky Very Large Array, a radiotelescope array in New Mexico, has discovered 13 supermassive black holes in dwarf galaxies. Most of the known supermassive black holes are found in large galaxies, with few known in dwarf galaxies. Astronomers were surprised to find that about half of the newly discovered black holes are not in the centers of the dwarf galaxies. Supermassive black holes in large galaxies are almost always located in the centers. Scientists believe that mergers with other galaxies pushed the black holes off center. These new discoveries are among the smallest galaxies known to harbor black holes. The discoveries were made by observing 111 small galaxies found in a visible-light catalog and also in a catalog of radio galaxies. Probably more of the 111 have supermassive black holes, but are not currently feeding on enough material to generate strong radio emissions.

Dark Matter Study – Dark matter is usually found by its gravitational influence on galaxies or clusters of galaxies. As a result, most known dark matter clumps are larger than galaxies. It was an unanswered question whether smaller clumps of dark matter exist. A new study using the Hubble Space Telescope observed eight distant quasars whose light passed through nearer galaxies, causing the quasar’s light to bend gravitationally and form multiple images of each quasar, a phenomenon known as gravitational lensing. Should the quasar light also pass through small clumps of dark matter as well, those small clumps would influence the appearance of the multiple quasar images. Two teams of astronomers at the University of California, Los Angeles and NASA’s Jet Propultion Laboratory found such differences in the multiple images, indicating that small dark matter clumps do exist. The clumps were calculated to contain one ten-thousandth to one one-hundred-thousandth the mass of the Milky Way’s dark matter. This amount of mass is likely small enough that many of the clumps couldn’t contain even a tiny galaxy, so these dark matter clumps could not have been found by conventional searches for dark matter. Scientists are interested in these clumps because they support the “Cold Dark Matter” theory, which says dark matter is made of relatively slow-moving particles, predicts that small clumps would have formed by gravitationally-induced collapses. The competing “Warm Dark Matter” theory predicts such clumps could not have formed.

Swan Nebula – A new study in infrared using the SOFIA flying observatory may have figured out how the Swan Nebula (also known as Omega or M17) got its unique shape. Astronomers at the SOFIA Science Center at NASA’s Ames Research Center found that the ages of various parts of the nebula formed at three different times. The central part is the oldest, followed by the northern area and finally the southern area. Essentially the shape is the result of three different, but adjacent, nebulas forming over time. The Swan Nebula is about 5,000 light-years away and contains over 100 very massive young stars. The new observations discovered nine new still forming protostars. SOFIA used infrared wavelengths different than those used in previous Swan observations, and was able to see more details within.

Tektite Crater – Tektites, glassy objects that resemble meteorites, are earthly surface material melted and splashed up by huge meteorite impacts. Much of the areas where tektites are found lie across a wide region centered on Southeast Asia, covering about 10 percent of the Earth’s surface. These tektites have been dated to about 790,000 years ago. But up until now, no impact crater of the right size, age and location that could have scattered these tektites has been found. Scientists now believe they have found that crater. Scientists led by researchers at Nanyang Technological University in Singapore found evidence of a crater about nine miles across in southern Laos. It had never been noticed before because it is covered by a lava flow, which was found to be the right age. Scientists plan to continue to study the lava flow, but no one has committed to drill down to the probable crater as of yet.

FRB Source Located – Astronomers with Canada’s CHIME Fast Radio Burst collaboration have located the source of a second repeating fast radio burst (FRB). The locations of most FRBs are hard to pin down because the bursts last only a tiny fraction of a second and are one-time occurrences, though a few do repeat. The discovery of this repeating source was made using the European Very Long Baseline Interferometer Network a widely-separated radiotelescope network with sites across the world. The newly located FRB source is in a star-forming region of a faint spiral galaxy about 500 million light-years away. This source is different than the first located repeating FRB, which was in a distant dwarf galaxy, though both are believed to be star-forming regions. In addition, two non-repeating FRB sources have been traced to large distant galaxies. It’s still unclear as to the cause or causes of FRBs. Scientists hope that because this newly located repeating FRB is closer than others, further observations may tell astronomers more about FRBs.