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

Dark Matter Mystery Solved – In 2018 and 2019, astronomers reported finding two small galaxies that appeared to have little if any dark matter. This is unusual as essentially all galaxies measured for it contain far more dark matter than ordinary matter. Further study led by researchers at the University of New South Wales of one of the galaxies, designated NGC 1052-DF4, using the Hubble Space Telescope and a ground-based telescope, shows tidal tails extending from it. This indicates that a close encounter with another galaxy gravitationally disrupted it. The observations imply that NGC 1035 is the guilty party, not NGC 1052, of which DF4 was thought to be a satellite galaxy. However, the core of DF4 is relatively undisturbed. The new study also found that the pattern of globular clusters about DF4 supported a past close encounter. Computer simulations of such an encounter show that it would gravitationally strip most of DF4’s dark matter halo first, then the outer starry parts of DF4, and lastly the core of DF4. Mystery solved: DF4 likely formed in the midst of a halo of dark matter, like every other galaxy, but was stripped of the dark matter by a close encounter with a more massive galaxy.

Very Young Jets – A team of scientists from the U.S. Naval Research Laboratory has discovered some of the youngest known jets being emitted from a supermassive black hole at the center of a distant galaxy. The jets were detected in 2019 by radio, using the Jansky Very Large Array radiotelescope in New Mexico, but were not seen in archived observations from about 20 years ago. Continued observations will allow astronomers to see how jets develop and what their influence is on the surrounding galaxy.

X-ray Bubbles – Scientists at the Max Planck Institute for Extraterrestrial Physics, using data from the eROSITA X-ray space telescope, have discovered a pair of structures located just above and below the center of the Milky Way. The northern structure, but not the southern one, had been detected before. The pair resembles similar structures seen in gamma rays, known as Fermi bubbles, discovered a decade ago, but are larger and lower in temperature. Likely the newly discovered structures were caused by a massive release of energy from the galaxy’s center some time in the past. The source of that energy could be a huge burst of star formation or an outburst from great amounts of material falling into the supermassive black hole.

Captured Stars Found – A team of astronomers at Liverpool John Moores University using positions, velocities and composition of stars from two huge star surveys, found about a thousand stars near the center of our Milky Way that must have been captured during a collision with a smaller galaxy about 10 billion years ago. They nicknamed the smaller galaxy Heracles. Another team announced a similar discovery recently, based instead on studies of globular clusters. Their colliding galaxy was nicknamed Kraken. It is not known if these two collisions are one and the same. Further study may tell.

Most Distant Galaxy – A team of astronomers at Peking University and the University of Tokyo, using the Keck Telescope in Hawaii took a spectrum of a galaxy seen in Hubble Space Telescope images that was thought to be very distant. The redshift found in the spectrum showed it to be the most distant galaxy known. Its redshift is 10.957, which indicates its light took 13.4 billion years to reach us. We are seeing the galaxy as it was merely 0.4 billion years after the Universe began with the Big Bang. Due to expansion of the Universe, its current distance is much larger than 13.4 billion light-years.

Lunar Sample – The Chinese space agency has landed another probe on the Moon, this one named Chang’e-5. It is solar powered, so was designed to achieve its mission in a single lunar daytime, which lasts 14 Earth days. It completed in this time its major goal of drilling and scooping lunar material into a sealed container and rocketing the sample to Earth. This is the first lunar sample returned since a Soviet mission in 1976. The landing area, near the mountain Mons Rümker, was chosen because it is a very young lunar surface, so gives scientists a sample of much younger age than any others. That area was flooded with lava only 1.2 billion years ago. The mission has other scientific capabilities, including a spectrometer and a ground-penetrating radar.

Juno, the orbiter circling Jupiter, has shed light on an issue that was raised by the Galileo Jupiter atmospheric probe 25 years ago. Scientists at Southwest Research Institute using data from Juno found the atmosphere that it descended through was much hotter and drier than the planet was believed to be. The best explanation was that the probe happened to hit one of a few atmospheric hot spots. However, Juno has found that Jupiter is full of hot spots, including the northern equatorial belt, a band wrapping entirely around the planet.

Asteroid Sample – Japan’s Hayabusa2 spacecraft sped by the Earth in early December and dropped its sample capsule off to land in the Australian desert. The reentry was even seen from the International Space Station. Hayabusa2 had collected two samples, one from the surface of asteroid Ryugu and the other from within a crater punched in the surface by a small bomb thrown at the asteroid. The latter sample should allow scientists to see what asteroid material was like when it formed more than four billion years ago, and compare it with the other sample that has been space weathered for most of that time. After landing and retrieval, the capsule was found to be correctly sealed, allowing even gas from the asteroid to be recovered. Weighing the capsule indicated that the samples weigh 5.4 grams. The mission far exceeded its stated goal of retrieving at least one tenth of a gram of material. Meanwhile, the spacecraft itself is on its way to flyby another asteroid in about six years, and a rendezvous for lengthy study of a third in about 11 years. NASA’s OSIRIS-REx mission will return a sample from another asteroid in 2023, so comparison with Hayabusa2’s sample will be made then.

Voyager Discovery – The Voyager 1 & 2 spacecraft, launched 43 years ago, continue to make discoveries. A team led by scientists at the University of Iowa have for the first time detected cosmic ray electrons in interstellar space that were linked to emissions from the Sun. Electrons moving near the speed of light were detected first, followed by somewhat slower electrons, and then a shock wave roughly a month later. All came from a coronal mass ejection (CME). Such CMEs are charged particles and electromagnetic energy expelled by the Sun. The electrons initially travel at about a million miles per hour, but are accelerated 670 times faster, to nearly the speed of light, by the shock wave.

Sun’s Fusion – Most of the nuclear fusion going on in the Sun is the proton-proton chain. In it, eight protons (which are hydrogen nuclei) smash together in a series of collisions and produce a helium nucleus while releasing 2 protons. Neutrinos are given off during this process, and neutrino detectors on Earth have been seeing since 2014 the right sort of neutrinos to verify this chain is actually happening. In addition, about 1 percent of the Sun’s energy should theoretically be produced by the CNO fusion cycle, so named because it involves carbon, nitrogen and oxygen, not just hydrogen and helium. For the first time, neutrinos given off in a CNO cycle in the Sun have been detected by the Borexino Collaboration verifying that this cycle is indeed happening in the Sun at the theoretical rate. Stars that are hotter than our Sun should be producing more of their energy by the CNO cycle.

Galaxy Rays – Researchers led by scientists at the Harvard-Smithsonian Center for Astrophysics found in a Hubble Space Telescope image rays of dark and light emanating from galaxy IC 5063, which is 156 million light-years away. It is reminiscent of crepuscular rays seen in some cloudy sunsets. The newly-found rays are produced by the glow of the accretion disk surrounding the galaxy’s central black hole shining around dense patches of nearby material.

Milky Way Center’s Distance – The best measurement of our Sun’s distance from the center of the Milky Way galaxy has been for decades 27,700 light-years. A new measurement by the VLBI Exploration of Radio Astrometry collaboration now sets that distance at 25,800 light-years. The new work was done using an array of radiotelescopes scattered across Japan. The positions and motions of 100 nearby stars were measured, and from this their orbits about the center of the galaxy were calculated. These measurements will continue, which should further reduce uncertainty about the distance to the galaxy center.

Data Release – The Gaia space telescope team has delivered its Early Data Release 3, which contains magnitudes, 3-dimensional positions and 2-dimensional proper motions for nearly 1.5 billion stars. Additionally, the full Data Release 3, planned for the first half of 2022, will have variable star data, temperatures, and extinction and reddening from interstellar material for a similar number of stars, and also a huge number of asteroids. The Early Release is complete (that is, contains all visible stars) between magnitude 12 and 17, and includes many stars to magnitude 21, but no stars brighter than magnitude 3 are present because they overload the telescope. Typical precision of position measurements are within 0.00002 arc second, and of brightness measurements within 0.0003 magnitude.