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

Supernova Age – A new analysis of a supernova remnant in the Small Magellanic Cloud by scientists at Purdue University shows that the supernova should have been visible in the far south of Earth 1,700 years ago, but no record has been found of it having been seen. The new analysis measured the speed of knots of material thrown out by the supernova, but only selected ones that appeared not to have been slowed by interference from other gas or dust. Their paths were then traced back to give the time of the explosion. Previous attempts to date this supernova using slightly different techniques have given widely differing age estimates. The speeds perpendicular to line-of-site to the remnant gas clouds were obtained from Hubble Space Telescope images taken 10 years apart.

Exoplanet Seen in Radio – Scientists from Cornell using data from the LOFAR array of radiotelescopes in Europe have detected bursts of radio emissions that are believed to originate from an exoplanet. If confirmed, it would be the first radio detection from a planet outside our Solar System. The planet orbits the star Tau Boötis and is about 51 light-years distant. It was discovered in 1996 and is known to be a gas giant. The radio signal resembled the kind emitted by Jupiter, but far weaker due to Tau’s distance. Other exoplanets were targeted in the search, such as the 55 Cancri system, but no significant radio signal was detected.

Polarized Planet Light – A team of astronomers at Leiden University has for the first time detected polarized light from an exoplanet. Polarized light has its light waves vibrate in only one direction. The planet orbits the star DH Tauri, located 437 light-years away. It is a gas giant with 11 times the mass of Jupiter. It is a young planet, only about two million years old, and is still glowing in infrared from the heat of planet formation. It is believed that the infrared glow is scattered off a disk of gas and dust surrounding the planet, and that scattering polarizes the light. The planet is also unusual in that it is located quite far from its star (ten times Neptune’s distance from our star), and that the disk around the planet is tilted with respect to the disk around the star. These quirks may be related, because astronomers believe that planets forming close to a star will have their disks form along the same plane as the star’s disk. The observation was made with an instrument on the Very Large Telescope in Chile that can block starlight to make it easier to see planets nearby. The study looked at 20 exoplanets, but the one orbiting DH Tauri was the only one showing polarization.

Outbursting Black Hole – ASASSN is a sky patrol searching for supernovas headquartered out of Ohio State University. Among the other things it has found is a galaxy whose central supermassive black hole repeatedly outbursts, which has been designated ASASSN-14ko. It has been imaged for several years at various spectrums of light. It is the most consistent such outburster, doing so about every 114 days, sort of an Old Faithful of black holes. Each outburst builds in brightness for about five days, then fades. Recent observations support the idea that there is a star in close eccentric orbit about the black hole, and every time it passes close to the black hole, pieces of the star are gravitationally torn off. That stellar material hits the accretion disk of the black hole and causes the bright outburst. Images from the TESS planet-finding space telescope were particularly helpful in understanding ASASSN-14ko because it took images every 30 minutes of an area that included the outburster while looking for planets transiting stars in that area. The galaxy is known as ESO 253-3, which is over 570 million light-years away in the constellation Pictor. The supermassive black hole has a mass of 78 million Sun’s masses. The galaxy surprisingly has two supermassive black holes, but the other one is not involved in the outbursts.

Shrinking Planets – It has long been thought that Neptune-sized planets, if warm enough, would slowly lose their atmosphere and shrink in mass and diameter. A new study by researchers at the University of Hawaii has confirmed this. The team used precise distances and colors of a selection of stars that host 2600 known planets to calculate the stars’ sizes and ages, then used planet transit data to determine the sizes of planets relative to the sizes of their stars. The Neptune-sized planets receiving great warmth from their stars were found to shrink over the course of a billion years or so.

Old Exoplanet – Astronomers at the University of Hawaii have discovered a rocky planet orbiting a very old star that is poor in heavy elements. The star is about 10 billion years old and has three known planets orbiting it, two being gas planets and one rocky. The latter is about 1.5 times the size of Earth. The star is known as TOI-561. The “T” in TOI stands for TESS, the planet-finding space telescope that discovered this planetary system. The rocky planet orbits so close to its star that it takes only about 10 hours per orbit and is heated by its star to over 3,000 degrees Fahrenheit. Most of the exoplanets known are in the thin disk of the Milky Way, but TOI-561 orbits in the thick disk, and is thus a bit out of the central plane of the galaxy. Some astronomers had surmised that it would be difficult for stars with very low amounts of heavy elements to form substantial planets, but this discovery shows that is not necessarily true.

Galaxy Evolution – When galaxies lose their cold gas, they stop forming stars and become “red and dead” galaxies; “dead” because they are not forming new stars and “red” because the remaining old stars are red. Hot gas will not collapse to form stars, so only the supply of cold gas matters for this process. Observations made by the ALMA radiotelescope array and analyzed by astronomers at the Saclay Nuclear Research Centre in France have discovered a galaxy that is rapidly losing its cold gas but has not yet stopped forming stars. Astronomers hope to understand how the process of becoming a dead galaxy occurs by studying this discovery. The galaxy, dubbed ID 2299, is losing gas with the mass of 10,000 Suns every year. It should be a dead galaxy in a few tens of millions of years. The loss of gas may have been triggered by a collision with another galaxy, since a faint tail has been found, which is characteristic of galaxy collisions. ID 2299 is so distant that we are seeing it as it was when the light left there about nine billion years ago.

High Velocity Stars – A relatively small number of stars within our Milky Way move at substantially greater speeds than the stars in roughly circular orbits around the galaxy. About 550 of these high velocity stars were known before a new study led by astronomers at the National Astronomical Observatories of China went looking for new ones, and found 591 more. Of these, 43 have such high velocity that they can escape the gravity of the galaxy and are known as hypervelocity stars. The data came from the LAMOST telescope in China and the Gaia astrometric space telescope. The new discoveries were located in the inner halo of the Milky Way and were found to be low in heavy elements. The researchers believe that these high velocity stars (and the Milky Way’s stellar halo generally) were acquired from dwarf galaxies that collided with our galaxy. Nearby dwarf galaxies contain many stars low in heavy elements, and these stars’ high speeds would result from their capture during a galaxy collision. Researchers hope that tracking of high velocity stars will allow astronomers to locate concentrations of dark matter in the halo of our galaxy.

Lithium Found – As the Universe cooled in the first few minutes after the Big Bang, the high temperatures and pressures created large amounts of hydrogen and helium with a little lithium. All other elements (and more helium) were forged later inside of stars, supernovas and stellar collisions. Scientists have calculated theoretical models  of element formation that match the amount of hydrogen and helium observed in the universe, but not enough lithium has been seen. However new observations likely found the missing lithium. The observations by astronomers at the University of North Carolina Chapel Hill, University of Montreal and Los Alamos National Laboratory of planetary system remnants crashing into white dwarf stars using spectral measurements showed lithium that’s hidden most of the time. They believe that the lithium from the Big Bang ended up inside planets and asteroids and the only time that observations can pick up that lithium is when the planets and asteroids collide with stars.

Rare Magnetar – Data from the Chandra X-ray space telescope has supported the idea that J1818.0-160, a magnetar discovered last March, is also a pulsar. A magnetar is a neutron star with an extremely strong magnetic field while a neutron star that every rotation gives off pulses of light, including radio or other wavelengths, is known as a pulsar. Astronomers from West Virginia University the University of Manitoba found the magnetar’s rate of changing spin energy into X-rays matched the rate exhibited by pulsars. This supported recent observations in radio that matched pulsar properties. This object is only the 31^st known magnetar, out of about 3,000 known neutron stars, and is only the fifth magnetar to be found to also be a pulsar. It is probably the youngest magnetar known, with an estimated age of only 500 years. It also is the fastest rotating magnetar known, with a period of 1.4 seconds.

Unusual Gamma-ray Burst –  A study by researchers at the University of California, Berkeley of a burst of gamma rays that lasted just a fraction of a second last April shows that the cause was not colliding neutron stars — the usual one for such bursts — but instead was a magnetar in the nearby galaxy NGC 253. Brief bursts of gamma rays have previously been attributed to magnetar activity, but only for magnetars located in our Milky Way galaxy. This means that magnetar bursts are inherently much weaker than colliding neutron star bursts in order to appear roughly the same brightness though the source is far closer. This new magnetar observation raises the question of whether some other gamma-ray bursts have been mistakenly attributed to the wrong cause. The correct cause can be distinguished using detailed profiles of the brightness level as a burst progresses.

Black Hole Activity – Astronomers at ASTRON trained two different radiotelescope arrays sensitive to different radio frequencies on a number of supermassive black holes. The LOFAR array was used for low frequencies and WSRT-Apertif for high. They found that differences seen at the various frequencies can tell whether a supermassive black hole is actively consuming large amounts of matter, or if it’s not active, how long it has been since its previous active period. Astronomers believe that active periods of supermassive black holes last tens or hundreds of millions of years, and that they probably repeat several times. This new result with differing radio frequencies will help scientists put together histories of black hole activity and test the beliefs about active periods.

Brown Dwarf Catalog – A team led by astronomers from Caltech has released the most comprehensive catalog of brown dwarfs in the Sun’s neighborhood. Brown dwarfs are stars that failed to have sufficient mass to sustain the nuclear fusion that powers ordinary stars. Much of the search work for this was done by volunteer citizen scientists participating in the Backyard Worlds program. The catalog has 525 brown dwarfs within 65 light-years of us, with their three-dimensional positions. A surprise is that there are roughly equal numbers of brown dwarfs and genuine stars in this neighborhood. Perhaps this is normal for all regions of the disk of our galaxy, but brown dwarfs are simply too dim to be found at any great distance away.

500-Meter Availability – In response to the collapse of the Arecibo radiotelescope, the staff of the Chinese 500-meter FAST radiotelescope of similar design has announced that they will now accept applications to use their telescope from astronomers outside China. Initially outside astronomers will be allocated 10 percent of observing time, but that may increase later. The FAST radiotelescope has roughly similar capabilities to that Arecibo had, except that FAST does not operate at quite as high frequencies and has no transmit capability, so cannot do radar. However FAST covers more of the sky because it can be aimed farther from the zenith than Arecibo could.

Missing X-rays – A stellar-mass black hole in a binary system known as GRS 1915+105 has been for decades gravitationally pulling material from its companion star at irregular intervals, producing bursts of X-rays. Then more than a year ago the X-rays stopped. Recent analysis by an astronomer at Villanova University shows that some object is blocking our view. Similar obscurations have been seen in other X-ray systems, but not lasting so long.

Lost Moons Found – In 2003 a team of astronomers used the 3.6-meter Canada-France-Hawaii telescope to search for small moons orbiting Jupiter and found 23 new ones. Because they were only tracked for a short time, their calculated orbits were not very precise, and over the years many of them were “lost” after not showing up where their imprecise orbit parameters predicted. Later search efforts eventually found all but five of the lost moons. An enterprising amateur astronomer, who has revealed only his first name Kenneth, decided to search for the still-lost five and found four of them. He used an online search system that finds archived images taken of a particular location in the sky at a particular time that should include a specified object with a given orbit. This yielded a few images that included some of the lost moons shortly before or after discovery. He then recalculated a more precise orbit using the newly found image positions. Eventually he was able to extend this method to recent images, so those moons were declared no longer lost. The most difficult of the four took about ten days at the computer to find. He found the most helpful images were taken by the same telescope that discovered the moons. This is probably because that telescope has an exceptionally wide field of view for a large telescope, so yields images of very dim objects in wide fields that are more likely to fulfill search requests. Coincidently two of the four found moons were also found independently by the original discoverer during the same time period.

Juno Extended – NASA extended the Jupiter orbiter Juno’s mission until September 2025. During the extension, its orbit will be changed to allow for the first time in its mission flybys of the moons Io, Europa and Ganymede, and to study Jupiter’s rings. It is standard practice for NASA to conduct such a review at the scheduled end of every space mission to determine if expending money to continue operation longer will result in scientific discovery worth the cost.

InSight Extended – NASA has also extended Mars lander InSight’s mission through December 2022. During the extension, InSight’s robotic arm will dig dirt and use it to cover the cable from the lander to its seismometer to reduce noise being picked up by that instrument. So far, more than 480 marsquakes have been recorded. The more marsquakes recorded, particularly the rarer large ones, the more scientists can calculate about the makeup of the interior of Mars. The extension recognizes the valuable science being done by the lander’s seismometer, weather station and planet wobble radio experiment, in spite of the failure of the heat probe that was to measure heat flowing from the planet’s core to the surface. That probe was designed to pound itself about five yards into the soil, deep enough to be unaffected by weather. After nearly two years of trying every means to get the probe to the desired depth, spacecraft controllers finally gave up after the probe had reached only its own length (16 inches) plus an inch below the surface. The failure was due to the soil on Mars having far different properties (principally lower friction) than every soil that the heat probe was tested on here on Earth.

Mars Sample Return – NASA approved moving ahead with their effort to return samples of Martian rock and soil to Earth. They’re coordinating with the European Space Agency (ESA) to share spacecraft missions to accomplish this. The ESA will provide a Mars orbiter with return-to-Earth capability, while NASA will provide a Mars lander with ascent-to-orbit capability. The NASA Perseverance Mars rover, landing February 18, was built with a drill and scoop to gather samples and seal them in containers. Perseverance or a future ESA rover will place the sample capsules in the ascent rocket. The samples should arrive at Earth in the early 2030s.

Proposed Missions – NASA has begun a program named Pioneers to build extremely low cost space missions under $20 million. The first four mission concepts were funded for planning, after which they will be reviewed to decide whether to build and launch. The four are: Aspera, which will study galaxy evolution and gas flow, using ultraviolet light; Pandora, which will observe 20 stars with planets to study planets’ atmospheric compositions, using visible and infrared light; StarBurst, which will observe high-energy gamma rays from sources including neutron star collisions; and PUEO, a balloon-launched mission to observe ultra-high-energy neutrinos emitted by black hole creation and neutron star collisions.

Novel Spacecraft Propulsion – A loaf-of-bread sized satellite known as MiTEE-1 is being launched to test a method of maintaining orbit without propulsion fuel. It will have two segments connected by a wire about a yard long, through which electric current from solar panels is passed. The magnetic field of that current will interact with the Earth’s magnetic field to apply a small force to the spacecraft. If it works, another spacecraft in the series will use a wire 10 to 30 yards long, which should provide sufficient force for a small satellite to maintain its orbit against the small drag forces of the Earth’s atmosphere at typical satellite altitudes. Small satellites are particularly prone to loss of orbit by atmospheric drag because of their small mass-to-area ratios. MiTEE-1 was built primarily by college students at the University of Michigan.

Lunar Goals – The NASA team assigned to establish science goals for the Artemis Moon landing released their report. The stated goals are:

• Understanding planetary processes
• Understanding the character and origin of lunar polar volatiles
• Interpreting the impact history of the Earth-Moon system
• Revealing the record of the ancient sun and our astronomical environment
• Observing the universe and the local space environment from a unique location
• Conducting experimental science in the lunar environment
• Investigating and mitigating exploration risks

The report further made many recommendations on how to achieve these goals, including that the astronauts be trained in geology and planetary science, that at least 330 lbs of lunar rocks and soil be returned, including subsurface and volatile (as in ice) samples, establishing long-lived power, communications and environmental monitoring capabilities at the landing site and creating a sustainable exploration program.