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

Earth-like Planet Found – An exoplanet has been found that is the closest yet to being the size and temperature of Earth. It was found by NASA scientists in archived Kepler data, and has been dubbed Kepler-1649c. It is 300 light-years away. It orbits its star at a distance that places it in the habitable zone, the area where the planetary surface temperatures are likely to allow liquid water to exist. It gets about 75 percent the amount of sunlight from its star as Earth gets from the Sun. It is 1.06 times the diameter of Earth, and is therefore quite likely a rocky planet. It is unknown whether it has an atmosphere. The star it orbits is a red dwarf star, much smaller and dimmer than our Sun. Red dwarf stars are known to often emit huge flares, though none has yet been seen from this one. A year on 1649c is a bit under 20 Earth days. Another rocky planet closer to this star was also found, but it is too warm to be in the habitable zone. The two planets orbit with a 4:9 resonance. That is, four of the outer planet’s years are nine of the inner planet’s years. This is an unusual resonance, prompting some astronomers to guess that there is an intermediate planet that is in 2:3 resonance with each, since 2:3 resonances are common (such as Neptune and Pluto). But no intermediate planet has yet been found. Teams analyzing Kepler data use a computer program called Robovetter to look through the millions of star dimmings recorded by Kepler to sort out the ones caused by planet transits from those caused by other phenomena. Only about one in eight observed dimmings is the result of a planet transit. A team of astronomers has been reviewing Robovetter’s decisions to find the program’s rejecting mistakes. The newly discovered planet was one of Robovetter’s mistakes found by this team.

Intermediate Mass Black Hole Found – Almost all the black holes that have been discovered are either “stellar mass” black holes (roughly the mass of a single star) or “supermassive” (millions or even billions of times the Sun’s mass). There are only a handful of known black holes with masses between these extremes. Collected data from the Hubble Space Telescope and X-ray space telescopes have produced the best evidence yet for an intermediate mass black hole (IMBH). In 2006, astronomers observed X-ray flares that could be explained from a number of different sources, including an IMBH tearing apart a star that passed too close. Subsequent Hubble observations pinned down the location of the X-ray flares to a star cluster in the fringes of another galaxy. This ruled out several of the other possible causes. The star cluster is possibly the stripped-down core of a dwarf galaxy, a place likely to find an IMBH. An international team of astronomers led by researchers at the University of New Hampshire believe that they have now ruled out all other causes for the observed X-ray flares except for an IMBH consuming a star. They then calculated the size of black hole necessary to emit the observed X-rays, and concluded that it is likely more than 50,000 times the mass of our Sun, solidly in the IMBH range. The astronomers looked through a large amount of X-ray observatory data before finding this one likely IMBH and plan to continue with the same techniques in hopes of finding more.

Very Distant Galaxy Imaged – Led by researchers at Japan’s Kindai University, astronomers were for the first time able to image gas clouds in a galaxy so distant that its light took 11 billion years to reach Earth. This was achieved using the powerful Chilean radiotelescope array ALMA, and was possible only because an intervening massive galaxy gravitationally lenses the light, magnifying it. Unfortunately gravitational lensing also distorts the image, so the astronomers had to digitally reconstruct what the distant galaxy really looks like. The team found that the clouds are being disturbed by the jets spewing out from the distant galaxy’s central, supermassive black hole. Further study is being planned in hopes that astronomers can find out if the jet disturbances are suppressing star formation in the galaxy.

Extremely Close Binary – A pair of helium-core white dwarf stars, known as J2322+0509, has been discovered orbiting each other quite closely by researchers from the Harvard and Smithsonian Center for Astrophysics, with colleagues at the University of Oklahoma and the University of Montreal. Though detached, that is, far enough apart that neither is gravitationally pulling material from the other, their period of revolution is only about 20 minutes, making it the third shortest period known for detached binary stars. Their orbit is nearly face-on to us, so one star would never appear to eclipse the other from Earth. This made it difficult to determine that this was indeed an orbiting pair of stars, but spectral observations uncovered their orbital motion. Their period is decaying as they lose energy by emitting gravitational waves. In six to seven million years, they will orbit so closely that they will merge into one massive white dwarf. The gravitational waves emitted by this pair should be detectable by LISA, a spacecraft mission scheduled to launch in 2034 to study gravitational waves, and will likely even be used to verify or calibrate LISA.

Binary Star Disks – Astronomers from the University of California at Berkeley used data from ALMA to study 19 planet-forming disks around binary stars. The study concluded that the planes of disks that formed around close pairs of stars tend to align with the planes of the stars’ orbit, but the farther apart the two stars were, the less aligned the planetary forming disks tended to be. The division between aligned and non-aligned occurs at about the size of orbits that have periods of 30 Earth days.

Nova Light Explained – A nova occurs when hydrogen pulled from a companion star accumulates on a white dwarf star until it ignites in a nuclear explosion. Astronomers generally attributed the visible flash of light to the explosion itself, but an alternate theory posits that shock waves from the explosion striking surrounding material actually emit the light. Gamma ray observations led by researchers at Michigan State University of nova V906 Carinae showed that shocks were creating the gamma-ray emission. Simultaneous observations in visible light and gamma rays showed their brightness varied in synchronization, implying the shocks contributed most of the nova’s visible light. The generation of light by shocks may well apply to supernovas and stellar mergers.

Quasar Jets Imaged – The Event Horizon Telescope (EHT) team generated the first detailed image of a black hole last year. Using the same techniques, the team has now produced an image of the center of a galaxy known as 3C 279 which also has a supermassive black hole at its core. It is too far away to image the black hole’s shadow itself, but instead shows jets emanating from the black hole in the best resolution yet. The black hole is located five billion light-years away in the constellation Virgo. The new image shows that the jet has a surprising twist near the base, which may be the result of shocks or instabilities. Features found perpendicular to the jet may be related to the accretion disk. Details of the image changed from day to day. The EHT technique is to tie together data from almost a dozen radiotelescopes spread across the face of the Earth to achieve resolution like a single radiotelescope the size of the Earth. This is known as very long baseline interferometry. Using this technique, the EHT has achieved resolution of 1/50,000th arc second.

Blazar Caught Forming – A “blazar” is the term for when the supermassive black hole in the nucleus of a distant galaxy is actively consuming matter and emitting bright, energetic jets, one of which is pointing directly at Earth. A leading theory is that these jets form when matter falls into the galaxy’s nucleus as a result of two galaxies colliding. A new discovery by an international team of astronomers led by researchers at Germany’s Deutsches Elektronen-Synchrotron DESY, appears to be just such a galactic collision that has prompted the activity and jets, supporting that theory. The collision has been examined by several Earth- and space-bound telescopes in various wavelengths to verify the observations. The jet’s age is estimated at just 15,000 years. Both galaxies with their separate central black holes are seen, and are in the process of merging.

Radio Strings – New images taken with the South African MeerKAT radiotelescope array of a galaxy with gigantic jets show three distinct magnetic plasma strings stretching out as long as 261,000 light-years. Few such strings have ever been seen, and none in such great detail. Researchers led by astronomers from Rhodes University in South Africa determined that the emission is from electrons emitting radio waves as they spiral in a magnetic field, known as synchrotron radiation. The three strings appear to be about the same age, but further work is needed to explain how these strings formed. The galaxy, known as ESO 137-006, is at the center of the Norma galaxy cluster, 220 million light-years away.

Brown Dwarf Wind – A team of astronomers at the Harvard-Smithsonian Center for Astrophysics have made the first ever measurement of wind speeds on a brown dwarf, and found them to be 1450 mph. The object is known as 2MASS J1047+21 and is about 33 light-years away. Brown dwarfs are larger than planets but smaller than stars. They lack the mass to compress their cores into sustained nuclear fusion, the process that powers stars. The team used radio and infrared observations to measure these wind speeds. The emitted radio signal varies over the object’s daily rotation, because it is affected by the object’s magnetic field, which rotates with the object’s core. The infrared emitted signals vary with rotating cloud patterns. By monitoring radio and infrared together, the core rotation and the cloud surface rotation periods can be measured. The difference is due to cloud surface wind speeds. The technique should also work on many exoplanets.

Exoplanet Atmosphere – Astronomers at Cornell University measured the spectrum of the atmosphere of the hottest known exoplanet, KELT-9b. It’s obit is nearly 30 times closer to its star than Earth’s is to the Sun, bringing its surface temperature to a sweltering 7,600 degrees Fahrenheit. The spectrum identified the presence of hydrogen and ionized calcium in the atmosphere, and allowed astronomers to gauge temperatures and pressures as well. The hydrogen was at a lower pressure placing it at a higher altitude than the calcium. The hydrogen was expected since the planet is a gas giant, but finding calcium is rarer, being only the second time it has been observed in a hot gas giant exoplanet.

Saturn Mystery Solved – A new analysis by Cassini’s Ultraviolet Imaging Spectograph team of the planetary probe’s old data has solved a mystery about gas giants. Though Cassini ended its mission to Saturn in 2017, new discoveries are still being made from its archived data. All four of the gas giant planets in our Solar System have layers high in their atmospheres that are hotter than can be accounted for from all known sources of heat. The new study compared the hottest places in Saturn’s atmosphere with images of auroras and found that the auroras are heating the atmosphere. Winds then distribute that auroral heat to the other areas. The same explanation may apply to the other gas giants.

Borisov Splits – The second object ever known to visit the Solar System from interstellar space, Comet 2I/Borisov, was observed to split into two pieces in mages taken by the Hubble Space Telescope. Such breakups are fairly common with ordinary comets. Soon after its discovery, astronomers observed Borisov moving too fast to have originated anywhere in the Solar System, and thus had to be from interstellar space. The breakup followed some observed brightenings, which are now attributed to the beginning of its breakup.

‘Oumuamua Explained – New computer simulations by researchers at the National Astronomical Observatories of the Chinese Academy of Sciences and the University of California, Santa Cruz, may have explained the strange properties of ‘Oumuamua, the first known interstellar visitor to our solar system. The researchers simulated a star tearing apart a planet, planetesimal or comet by tidal forces and found that the resulting shards are often long and thin, much like ‘Oumuamua. The shards are also often baked by their star, resulting in the surface being devoid of water and other volatiles, though water ice can persist deep inside. This would explain how ‘Oumuamua veered off its expected orbit as if jetting out water vapor as it warmed near the Sun, though no volatiles were detected. The surface baking also stiffens up the surface material, making a shard more able to keep its long shape without breaking up further. The shards are often thrown out of their own planetary system, eventually visiting other systems.

Betelgeuse – After the star faded over the last few months to its dimmest recorded level, it then crept back up to its former brightness over a period of about six weeks.

Solar Threads Discovered – A project named Hi-C has been occasionally launching a solar telescope above the atmosphere on sounding rockets, obtaining high-resolution solar images. The latest flight produced images analyzed by researchers at the University of Central Lancashire showing a previously unknown feature consisting of extremely fine magnetic threads made of million-degree plasma. The next Hi-C launch is coordinated to take data simultaneously with the Parker Solar Probe and Solar Orbiter space telescopes.

Bepi-Colombo – The joint European-Japanese mission to Mercury flew by Earth on April 10, in order to use our planet’s gravity to fling it toward the inner Solar System. It tested its instruments by observing the Earth and Moon during the flyby. Images were taken of the Moon using thermal infrared wavelengths to identify minerals present. It will take two flybys of Venus and six flybys of Mercury before settling into orbit around Mercury in late 2025. The mission is named after the Italian engineer who designed the orbit of the American Mariner 10 spacecraft so that it encountered Mercury three times between 1974 and 1975.

Astronauts Return – Astronaut Jessica Meir returned to Earth from the International Space Station (ISS) on April 17 after spending 205 days in space. She participated in the first three all-female spacewalks during this mission. Also returning in the Soyuz capsule were astronaut Drew Morgan and cosmonaut Oleg Skripochka. Morgan spent 272 days in space. Four of his seven spacewalks on this mission were to work on the Alpha Magnetic Spectrometer, which is searching for evidence of dark matter from its location on the outside of ISS. Skripochka spent 205 days in space this time, bringing his total days in space to 536.

American Spacecraft with Crew – The next astronauts to arrive at the ISS, Robert Behnken and Douglas Hurley, are scheduled for May 27 aboard a SpaceX Dragon Crew Capsule. This will be the first crewed American spacecraft to launch into space since the Space Shuttles were retired in 2011. Both crewmembers have previously flown on a Shuttle to the ISS. Boeing also has a privately developed crewed spacecraft almost ready to fly, but problems during their test flight in December have required one more uncrewed test flight before taking people to the ISS.