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

New Target For Lucy – The Trojan asteroids are found in two groups along Jupiter’s orbit, one group at a 60 degree angle ahead of the giant planet, and the other 60 degrees behind. These are two of the planet’s Lagrange points, where the combined gravity of the Sun and Jupiter create stable areas in which small bodies may orbit. The Lucy spacecraft, now under construction, is planned to be the first to visit a Trojan. Lucy was designed to visit six of them over a period of 12 years, as well as a main-belt asteroid on the way. New observations of the targets by researchers at Southwest Research Institute with the Hubble Space Telescope discovered that one of them, Eurybates, has its own small satellite, so the mission just got another target for free. The satellite was not noticed previously because it is 6,000 times dimmer than Eurybates. From this low level of brightness, it is estimated that the satellite is only about a half mile across. Launch is planned for 2021.

Comet Color – Analysis of the data from the Rosetta spacecraft shows that Comet 67P/Churyumov-Gerasimenko changed color as it changed position in its orbit about the Sun. The comet’s coma got redder and its nucleus got bluer while the comet was close to the Sun, and those colors reversed when far from the Sun. Researchers at Italy’s National Institute for Astrophysics determined that heat from the Sun caused reddish dust to be blown off the nucleus and into the coma. In colder times dust settled back onto the nucleus. Rosetta spent 2014 through 2016 orbiting that comet.

Pluto Winds – Computer simulations by researchers at NASA’s Ames Research Center have explained the winds on Pluto. The left side of the prominent heart-shaped feature on Pluto is a huge impact crater filled with nitrogen ice. Over the length of Pluto’s day, which is about six Earth days long, the nitrogen ice gets enough solar heat to turn into gas which then refreezes at night. This drives winds all over Pluto, including a spiral pattern over the nitrogen ice. Because Pluto’s axis is quite inclined, the heating pattern changes with its seasons, varying the wind patterns.

Proxima Exoplanet – Astronomers at the INAF Astrophysical Observatory of Turin think they have found a second exoplanet orbiting Proxima Centauri, the nearest star to our Sun, at a little over four light-years distance. Though technically a planet candidate until confirmed, astronomers believe that its mass is about half that of Neptune, and its orbit is about 1.5 times the diameter of Earth’s orbit. This means that its orbit is so far out that its temperature is very likely too cold for liquid water to exist on the planet. The star’s starspot activity added to the difficulty of finding this planet. The first planet orbiting Proxima was found in 2016.

Planets In Globular Clusters – A new study by Melissa Cashion of Texas A&M University simulated stars and their planets located in dense globular clusters. The study found that most planets were gravitationally flung away from their stars, but only a few of those ended up orbiting other stars. Most just wandered in the space between stars. Somewhere between 5 and 20 percent of planets survived billions of years still orbiting their original stars.

Hottest Exoplanet – A new study led by researchers from the University of Chicago of KELT-9b, the hottest known exoplanet at about 7,800 degrees Fahrenheit, shows that the heat there is breaking up the hydrogen molecules in its atmosphere into separate atoms. The planet is tidally locked, meaning one side is always facing toward the star. The broken-up hydrogen drifts to the night side, where cooler temperatures allow the atoms to recombine into molecules. This process distributes heat from the hot side to the cold side more quickly than winds alone could. KELT-9b orbits its star every 1.5 Earth days and has about three times the mass of Jupiter.

Young Planet Discovered – Scientists at Rochester Institute of Technology announced the discovery of a very young massive exoplanet only 330 light-years away. It is about ten times the mass of Jupiter and orbits a star known as 2MASS 1155-7919. The star is about five million years old, so the planet is very young. Its orbit is 600 times the size of the Earth’s orbit. Astronomers are trying to figure out how it formed or moved to a place so far from its star.

Binary Brown Dwarfs – Volunteer citizen scientists using Backyard Worlds: Planet 9, an online project by the American Museum of Natural History, have discovered a rare pair of brown dwarfs orbiting each other. Brown dwarfs are stars that lack sufficient mass to sustain nuclear fusion. These are over 30 billion miles apart, so it is surprising that they have never encountered anything that would gravitationally disturb and separate the pair. The brighter of the pair had been previously seen by the Gaia spacecraft, and determined to be 78 light-years away. They are 34 and 72 times the mass of Jupiter.

Binary Stars Required For GRBs – Long gamma-ray bursts are known to be caused by massive stars reaching the ends of their lives and exploding as supernovas, leaving behind a neutron star or black hole. A new study by astronomers at the University of Warwick using computer simulations of stars shows that the conditions to make such a gamma-ray burst occur only when the massive star has a companion star orbiting it closely. Tidal forces from the companion keep the star spinning during the explosion and cause jets of material to be thrown out, necessary conditions for the burst.

Low Mass White Dwarfs – Scientists at the Harvard & Smithsonian Center for Astrophysics have completed a spectrographic study of low-mass white dwarf stars. These have been a mystery because the lower a star’s mass, the longer it spends in its main sequence stage before becoming a white dwarf. However according to models, the lowest-mass stars like the ones that would have produced these white dwarves should have spent longer than the age of the universe in their main sequences. Yet these white dwarves exist. The best theory for their existence has been that some stellar companion star stole mass from them after they became a white dwarf. The new study supports this because every low-mass white dwarf studied was found to be part of a close binary star system. A total of 98 binary white dwarf systems were discovered during the study. From the number of these that were close enough to be found, the team estimated that there are 100 million white dwarf binaries in the whole Milky Way. The LISA mission, planned for launch in 2034, is a space-based gravitational wave detector that will be sensitive to waves emitted by close binary stars, and may add another way to study them.

Disk Shadow – In 2018 an image taken by the Hubble Space Telescope showed a shadow near the star HBC 672. It was believed to be caused by a planet-forming disk about the star. Such a disk would be too small to see, but the shadow is much larger, stretching roughly a quarter of a light-year. Recent observations by astronomers at Space Telescope Science Institute show that the shadow has moved, probably because the disk wobbled. Astronomers plan to keep observing the shifting shadow to see what they can learn about planet-forming disks.

Galaxy Halo Studied – A new study led by researchers at The Ohio State University measured the effects of gas on X-ray light emitted by a distant blazar, a very active galaxy core emitting blazing light, as the x-rays passed through the halo of our Milky Way galaxy. Those effects yield the temperature and composition of the gas. Scientists were surprised that the temperature ranged up to 10 million degrees, and found more heavy elements than expected. Those heavy elements, which included neon, oxygen, iron and others, had to have been formed by stars in the galaxy, indicating that more of the material from stars is flung out into the galaxy halo than expected. These observations were made with the XMM-Newton X-ray space telescope.

Galaxy Wave – A new three-dimensional study by an international team of astronomers of the locations of star-forming regions in the Milky Way has found a wave in this material that passes just 600 light-years away from us and stretches 9,000 light-years long. Its peaks and troughs reach about 500 light-years above and below the galactic plane. It constitutes much of the Local Arm, the section of galaxy spiral arm that contains our solar system. Theorists are working to explain how the wave formed.

Gamma-ray Sources – The HAWC gamma-ray observatory in Mexico is sensitive to higher energy gamma rays than other gamma-ray observatories. Its catalog of gamma-ray sources includes some sources that were missed by other observatories. Among these are nine newly announced sources of gamma rays, all of which appear to be associated with pulsars. The announcement by the HAWC collaboration also included some of the highest-energy gamma rays ever recorded. These discoveries not only help astronomers figure out what cosmic phenomena emit gamma rays, but what emits cosmic rays. Cosmic rays are actually charged particles, not forms of light like gamma rays. Interstellar magnetic fields deflect charged particles, making it extremely difficult to pinpoint the sources of cosmic rays. However, cosmic rays that collide near their sources produce gamma rays that appear to come from that same source, allowing astronomers to learn about cosmic rays from the gamma rays they produce.

Repeating FRBs – The majority of fast radio bursts (FRB) occur only once, but some of them repeat from the same location. Now one of the one-timers has been found to repeat. This was announced by the Australian group led by scientists at the Swinburne University of Technology who continued to watch the location of a strong burst from 2017. No additional signals were seen using the Australian Square Kilometer Pathfinder Array, but much fainter bursts were found using more sensitive big dish radiotelescopes. Another announcement by a different group led by scientists at the University of British Columbia found a repeating fast radio burst that is the first known to follow a regular pattern. It’s active about hourly for four days, then is quiet for twelve days. Located in a spiral galaxy about 500 million light-years away, it’s relatively close for an FRB.

A Supernova Explained – Researchers led by astrophysicists at Stockholm University have finally identified unusual spectral lines that were seen in the light of supernova 2006gy. These researchers were the first to compare the lines with known lines of neutral iron, rather than ionized iron, because no one expected neutral iron in a supernova. These neutral iron lines had never been seen in any supernova. This supernova was one of the brightest ever seen, in a class known as superluminous supernovas. The mass of iron necessary to make the lines observed is huge: at least a third of a solar mass. Computer simulations of supernovas showed that the only way to make so much iron and such a bright explosion is when a hydrogen-rich massive star has a companion white dwarf star orbiting it. The massive star expands near the end of its life, engulfing the white dwarf, which then spirals toward the center of the massive star. Material falling onto the white dwarf causes it to explode as a Type Ia supernova while inside the massive star.

Mapping Around a Black Hole – Astronomers would like to observe material falling into a supermassive black hole, but this area is just too small to resolve with any telescope. A new technique has been developed by astronomers at the University of Cambridge to map out the area around such a black hole. When a chunk of material falls in, it heats up and gives off a burst of light, including X-rays, which echo off the surrounding features. By observing the timing and other characteristics of the echoes, a map can be built of those features. This was done for the first time, using the XMM-Newton X-ray space telescope observing the supermassive black hole at the center of a galaxy cataloged as IRAS 13224-3809. It is one of the most variable X-ray sources, providing plenty of bursts to cause echoes. The observations also allowed astronomers to calculate the mass and spin of the black hole. The map showed a disk of matter lying in a corona of billion-degree matter, as expected. A surprise was that the corona changed size in just days. Astronomers plan to use the technique on other rapidly-varying active galaxy cores.

New Solar Telescope – The Daniel K. Inouye Solar Telescope has produced its first images, showing more detail of solar convection cells and other surface features than ever before. It does this by using a four-meter mirror, adaptive optics to compensate for motions in the Earth’s atmosphere and a massive heat dissipation system. The telescope is located atop the dormant volcano Haleakala in Hawaii, and is named after the late senator from that state. In addition to imaging, it has instrumentation to map magnetic fields in the Sun’s corona. Researchers expect to produce more solar data in the next five years than all solar data collected since the invention of the telescope.

Spitzer Retired – The Spitzer infrared space telescope has been retired. It was turned off late in January. It produced spectacular data for 16 years in spite of it being originally planned for a two-year mission, and having run out of coolant after five years. One of its three instruments partially ran without coolant, so it was able to continue observations more than a decade longer. Retiring Spitzer at this time was based on the increased difficulty of operating the aging telescope and on the estimate that it would be replaced by the James Webb Space Telescope by now, but which  has been delayed until next year. Spitzer is one of the originally planned four Great Observatories in space (along with the Hubble Space Telescope, the Chandra X-ray Observatory and the Compton Gamma Ray Observatory), designed together to cover infrared, visible light, ultraviolet, X-rays, and gamma rays. Spitzer made important discoveries about comets, asteroids, rings, dust, star and planet formation, and galaxies and their evolution. Some of the areas it contributed to were not even thought of when Spitzer was designed. Researchers will likely continue to make discoveries for many years by studying the archived Spitzer data.

General Relativity – Among other predictions, general relativity says that space becomes twisted around a rotating massive object, a concept called frame-dragging. A new study by astrophysicists at Stanford University of a white dwarf and a pulsar in a tight orbit around each other has been able to measure the frame-dragging around them. The extreme regularity of pulses from the pulsar allowed precise determination of this pair’s orbit. The orbit wobbles (or precesses) in a manner that depends on the frame-dragging occurring near the spinning white dwarf. Astronomers have observed the pair for 20 years, so there was plenty of data to work with. The white dwarf was found to rotate every 100 seconds. The pair is 12,000 light-years away, and they orbit each other every five hours.

Record Space Stay – Astronaut Christina Koch returned to Earth from the International Space Station, setting the record at 328 days for the longest stay in space by a woman. This is only 12 days short of Scott Kelly’s American record. During her time there, she conducted six spacewalks, including the first all-female spacewalk.

New Radio Dish – NASA broke ground to construct another radio dish in its Deep Space Network which will bring to 13 the number of operational dishes. This network is used to communicate with spacecraft in deep space as well as conduct radio astronomy and radar astronomy. This one will add to the group at Goldstone in the California desert. It will also have laser communication ability as well as radio.

Betelgeuse – Not only is Orion’s shoulder star Betelgeuse getting dimmer, it is apparently changing shape. Images taken with the Very Large Telescope in Chile using adaptive optics and analyzed by astronomers at Katholieke Universiteit Leuven resolved the star and show this changing shape. One possible explanation is that the star is being obscured by dust, but other causes are being examined.