Milky Way Black Hole – An international collaboration of astronomers released the first detailed image of the black hole at the center of our Milky Way galaxy, known as Sgr A*. Event Horizon Telescope consortium is the same that three years ago imaged the black hole at the center of galaxy M87, known as M87*. The observations for both black holes were made about the same time, but it took extra time to process the Sgr A* image because of the difference in apparent speed of rotation of the disks about the black holes. The Sgr A* disk rotates in minutes, while M87* disk takes many days because M87* is roughly 1,000 times the diameter of Sgr A*. The team had to develop processing techniques that compensated for the rotation of the Sgr A* disk during the days-long time exposures. The disk of gas around the black hole is seen distorted by the extremely strong gravity of the black hole, which bends light. The observed disk size exactly matches calculations made using Einstein’s General Relativity. The observations of both black holes were made with the Event Horizon Telescope, which combined the signals of eight radiotelescopes scattered across our planet, yielding resolution equivalent to a telescope the size of the Earth and hundreds of times better resolution than any space telescope.
Ingenuity – On May 3 the rover Perseverance lost radio contact with the Mars helicopter Ingenuity. Mission control operators determined that Ingenuity shut itself down when its battery charge became too low due to dust in the air reducing sunlight hitting the solar panel and heavy use of battery power by internal heaters. After sunlight levels increased a few days later, Ingenuity came back to life, but with its clock wrong. Spacecraft controllers did not know when Ingenuity would make its scheduled radio report to Perseverance, so they told the rover to listen all day for the report. Eventually it was heard and contact reestablished. Controllers changed parameters regulating helicopter internal heaters to reduce the chances of repeating the loss of contact. In total, Ingenuity has completed 28 flights and traveled over 4.2 miles.
Marsquakes – The InSight Mars lander’s seismometer has recorded more than 1,300 marsquakes, for more than three years, but the three strongest quakes have only recently been recorded. Strong quakes are important because they provide more information about the interior structure of the planet. These strong quakes were above magnitude 4, and one of them about magnitude 5. These are not large compared to earthly quakes, but Mars was expected to have much weaker seismic activity. The strong marsquakes included ones originating on the far side of Mars which traveled through the planet and were partially blocked by the core, giving scientists more information about the planet’s deep interior. One originated near Valles Marineris, the largest canyon in the Solar System, indicating that region has seismic activity. One of these strong quakes shook for 94 minutes, a new marsquake record.
InSight – NASA announced that accumulating dust on InSight’s solar panels has drastically reduced the amount of electrical power available to run the craft’s instruments. They are expecting to have to shut down the seismometer by late summer, and the whole spacecraft by the end of the year. Only a dust devil or other strong wind hitting the solar panels could save it. NASA has already tried techniques including shaking the panels to try to clear dust.
Dry Ice Glaciers – A new study by the Planetary Science Institute of the dry ice caps at the south pole of Mars shows that the frozen carbon dioxide they’re composed of flowed like glaciers. The evidence for flow is that the dry ice accumulated thicker in low areas forming basins and troughs, but likely deposited more uniformly in thickness originally. Dry ice began being deposited around the pole about 600,000 years ago due to a colder time in long-term climate cycles. The longest dry ice glacier found in this study is about 125 miles long by 25 miles wide. The study looked at the properties of dry ice and determined that under Martian conditions the dry ice glacier flow should be about 100 times as fast as water ice flow. Water ice is also present at the Martian south pole but does not appear to be flowing like glaciers.
Asteroids Found – Astronomers at the Max Planck Institute for Extraterrestrial Physics developed a program using humans and computers to find the tracks of asteroids that intruded on images taken by the Hubble Space Telescope. Applying this to 19 years of archived images found tracks of 1,701 asteroids, of which about one third were identified as known asteroids. Further work is planned to see what can be learned from these tracks regarding the asteroids’ distances and orbits.
Neptune Cools – A study by astronomers at the University of Leicester of two decades of archived infrared observations of Neptune, made by ground- and space-based telescopes, shows that the average temperature of its upper atmosphere dropped by about 14 degrees Fahrenheit, though near the south pole it has warmed 20 degrees Fahrenheit in the last few years. Astronomers had expected simple seasonal changes in temperature, which would have seen the entire southern hemisphere warming. Neptune’s year is so long that each of the four seasons takes about 40 Earth years, so this study spanned only a half season.
Planet-Forming Disks – A team of astronomers from the Max Planck Institute for Astronomy used the ALMA radiotelescope array to study 870 planet-forming disks in the Orion A cloud. They believed that the presence of nearby massive stars could disturb such disks, so they eliminated such cases from the study. They found that the total mass of small particles in the disks steadily declined with age. Within just a few million years of forming, disk masses decline substantially. This implies that if planets are going to form, they do so within a few million years. The study did not establish whether the particles disappearing with age had gone to form planets, had migrated into the star, or had evaporated from heat.
Black Hole Growth – Astronomers at Washington State University using the Chandra X-ray space telescope studied 108 galaxies that have dense star clusters at their centers. They found that the denser the star clusters were, the more likely they contained a black hole feeding on star material falling in. This may explain how stellar-mass black holes, which are created by massive stars reaching the ends of their lives and collapsing, grow to intermediate-mass or larger black holes.
Magnetic Reversal – Astronomers at the University of Maryland have been watching a galaxy in Draco known as IES 1927+654 in X-rays, ultraviolet, visible light, and radio using various space- and ground-based telescopes. In 2018 the galaxy brightened by nearly 100 times in visible light, and brightened in ultraviolet as well. Subsequently the high-energy X-rays disappeared, and then returned four months later. The theory that best explains the observations is that the magnetic field of the galaxy’s central black hole reversed with its the north and south magnetic poles swapping places.
Black Hole Echoes – As matter falls into a black hole, often from a closely orbiting companion star, friction heats the matter until it emits X-rays. If there is other material nearby, the X-ray light can echo off that material. Astronomers at the Massachusetts Institute of Technology developed an automated search tool to find these echoes in X-ray telescope observations. They found eight new X-ray echoes when applied to observations from the NICER X-ray telescope on the International Space Station. Only two such echoes in our galaxy were known previously. They found a pattern to such systems: the black hole emits a jet of high-speed particles, then gives a high-energy flash, and finally drops to low energy emission. Astronomers use such X-ray echoes to learn what material lies where in the vicinity of the black hole, and are pleased for the new echo discoveries.
Black Widow Binary Discovered – A “black widow binary” is a pair of stars in which one star is a neutron star that is gravitationally eating its companion star. Only about two dozen of them are known in our galaxy. A new one has been apparently discovered by astronomers at the Massachusetts Institute of Technology, though it’s not yet confirmed in X-ray or gamma rays. Known as ZTF J1406+1222 and about 3,000 light-years distant, it has the fastest orbital period of any known black widow binary, at 62 minutes. It is actually a triple star, though the third is quite distant, taking 10,000 years to orbit the close pair. Previous black widow binaries have been found by the X-ray or gamma ray radiation emitted by the neutron star, but astronomers discovered this by the visible light pulse emitted by the hot side of the companion star on each orbit. The radiation from the neutron star makes one side of its companion much hotter. The astronomers were specifically looking for such hot-side pulses in archived data from the Zwicky Transient Facility, a project using the large Schmidt telescope at Palomar. The search also found a dozen known black widow binaries, demonstrating the viability of this search technique.
Hydrogenless Supernova – Astronomers from the Space Telescope Science Institute using the Hubble Space Telescope discovered a faint companion star that withstood the recent supernova explosion of its binary partner star. The supernova, which occurred in 2013, didn’t show any hydrogen spectra, meaning that before it exploded the star had been stripped of its hydrogen outer layer. This is the best evidence yet for the theory that hydrogenless supernovas occur when a closely orbiting companion star gravitationally steals the primary star’s hydrogen layer. The companion was found in ultraviolet light, and had become detectable as the glare from the supernova faded. During the nova, astronomers observed ultraviolet light peaking in brightness twice, and they now attribute the second peak to the shock wave hitting the companion star.
Nova In X-rays – Astronomers at the Friedrich-Alexander-Universität were using the eROSITA space telescope to observe a white dwarf star in low energy “soft” X-rays when the star exploded. The flash lasted less than eight hours and was so bright that it overloaded the sensors in eROSITA. The astronomers believe that the explosion was caused by hydrogen drawn from a companion star accumulating on the surface of the white dwarf until it reached the temperature and pressure to fuse into helium. This is the same cause as ordinary novas seen in visible light, so they believe that this X-ray flash is the first stage of a nova. A nova’s visible light is emitted by the cloud of gas blown away from the explosion that cools to temperatures which glow in visible light and can last for weeks or months. A similar visible glow was seen at the star that eROSITA observed, but beginning a half day later. Astronomers now think that they’d missed the X-ray flash prior to the visible glow of novas because there have been few X-ray telescopes sensitive to soft X-rays, soft X-rays are more easily blocked by interstellar medium, and the X-ray flash doesn’t last long.
Starliner – A Boeing CST-100 Starliner space capsule launched from Florida and docked with the International Space Station for a stay of approximately four days. The Starliner carried only cargo on this trip but it’s designed to ferry up to four astronauts. With this success the United States is closer to being able to send passengers to the ISS from multiple carriers, the other being SpaceX.
LHC Restart – CERN restarted its Large Hadron Collider (LHC) after a more than three-year shut down for hardware upgrades. The new components allow the accelerator to apply more energy to the particles that it smashes together and to increase the capabilities of its particle detectors. It is scheduled to take data on subatomic particles over the course of its new four-year run.
Missions Extended – After a careful review, NASA extended the missions of eight of its spacecraft that had been scheduled to run out of funding this year. Mars Odyssey, Mars Reconnaissance Orbiter, MAVEN Mars orbiter, Curiosity Mars rover, InSight Mars lander, Lunar Reconnaissance Orbiter, OSIRIS-REx asteroid sampler and New Horizons will continue to operate and collect data. OSIRIS-REx, after it delivers to Earth its collected samples of material from asteroid Bennu, will be given a new target, Apophis, an asteroid that will closely flyby Earth in 2029. It will orbit this new target, but not obtain a sample of it. InSight will continue to take seismic and other data on Mars until the end of this year, depending on how long its power holds out. New Horizons will continue to explore the Kuiper Belt beyond Pluto, though no new target body has been found suitable for a close flyby.
