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

Most Massive Black Hole Merger – The largest black holes ever observed to merge were detected by the LIGO and Virgo gravitational wave detectors. The black holes were 85 and 66 times the Sun’s mass and merged to form one of 142 solar masses. The excess of about eight solar masses was converted into the energy contained in the gravitational waves. The event occurred at a distance with a light-time travel of 10 billion years. The distance to it now is considerably more at about 17 billion light-years due to the expansion of the Universe that occurred while the gravitational waves were traveling to Earth. What’s remarkable about this observation is that astronomers don’t know how black holes can form with masses of 85 and 66. Based on the black holes LIGO and VIRGO have seen merging, it was thought that essentially all stellar-mass black holes are below 43 solar masses. It was thought that stars above that threshold die in a “pair-instability supernova” where antimatter produced in the supernova blows the entire star apart rather than collapsing to a black hole. After seeing this new merger, theorists are working on how black holes can form or grow to more than 43 solar masses.

Lunar Hematite – During much of the Moon’s orbit around Earth, our satellite is outside the Earth’s protective magnetic field, and so is bombarded with hydrogen ions thrown off the Sun. This bombardment prevents metals on the Moon’s surface, such as iron, from forming oxides, including common iron rust. So it came as a surprise when data from the Indian lunar orbiter Chandrayaan-1 showed hematite, a form of iron oxide, in several locations on the Moon. A new study by researchers from the University of Hawaii shows that this has occurred because oxygen is being thrown off the top of Earth’s atmosphere and is hitting the Moon, particularly when the Moon passes through our planet’s magnetic tail. The water ice known to be found in certain areas of the Moon probably also takes part in the formation of the hematite, and the locations where the hematite was found support this theory.

Phosphine – An international team of astronomers led by researchers from Cardiff University using two different radiotelescopes have found the spectral lines of the chemical phosphine in Venus’s atmosphere, in very small concentrations. It’s significant because most phosphine in Earth’s atmosphere is emitted by living things. There are non-life processes that produce phosphine, but the astronomers involved stated that they did not know of a non-life process that would be likely to occur on Venus and would produce the amount of phosphine measured. There have been theories proposed that Venus in the distant past may have had oceans and climate that could allow microbial life to develop, but today its surface is far too hot, dry and acidic for life as we know it. There are theories that microbes could still live in the conditions found high in Venus’s atmosphere where the temperature is more reasonable, but there is little direct evidence to support this. It’s an intriguing find, but in no way conclusive evidence of life. There is probably little that scientists can do to find the source of the phosphine until a new space probe visits Venus with different instruments.

Europa’s Surface Moved – A study by astronomers at the Universities Space Research Association of the cracks in the icy surface of Jupiter’s moon Europa shows that sometime in the last several million years its surface moved more than 70 degrees in latitude in relation to its rotational poles. The study used archived images from the Voyager and Galileo spacecraft. The cracks are formed in predictable shapes and locations by tidal forces. The movement of the surface should cause other features that would be visible in higher resolution images, and so this theory can be checked by the upcoming Europa Clipper mission, planned for a 2024 launch.

Jupiter Moons – A couple of years ago, a search around Jupiter brought the total of its known moons up to 79. A new search by researchers at the University of British Columbia using a more sensitive technique, found an additional 45 tiny objects near Jupiter that are likely moons. The researchers stacked multiple exposures, offset by every amount a moon was likely to orbit in the interval between exposures. The stacking brings out even dimmer objects. The technique was applied to a series of 60 archived images taken years ago by the Canada France Hawaii Telescope in Hawaii. The astronomers extrapolated, based on the prevalence of moons in the small area they searched, that there may be roughly 600 moons orbiting Jupiter, most still to be discovered, and likely far more too small to be detected. The objects found range down to about a half of a mile across. The astronomers involved do not plan to spend the observation time necessary to track these objects and verify that they are indeed previously unknown moons of Jupiter. Once it’s completed, routine operation of the Vera Rubin Observatory will make observations that are likely to verify these and additionally cover the rest of Jupiter’s orbital zone. That observatory is scheduled to begin imaging the entire visible sky every few nights starting next year.

Andromeda’s Gaseous Halo – Astronomers from the University of Notre Dame studied the hot gaseous halo surrounding the Andromeda Galaxy by observing the spectra of 43 quasars whose light shines through that halo. The gas is so sparse that there is no means to “see” it other than its effects on light passing through. Using the ultraviolet spectrograph on the Hubble Space Telescope, the team found that the halo has two nested shells with the outer shell smoother and hotter than the inner shell. The halo stretches 1.3 million light-years toward us and as much as two million light-years in other directions. If the Milky Way’s gas halo is of a similar size, then the two galaxy’s halos are bumping into each other already even though the collision of the two galaxies is about 4 billion years in the future. If the Andromeda gaseous halo were visible, it would appear to be by far the largest object in the sky, stretching about a dozen times as long as the star-filled part of the Andromeda galaxy. Studying this halo will help astronomers understand how such gas contributes to star formation and how it contains outflows from violent events in the galaxy.

Dark Matter Halos – Halos of dark matter surround clusters of galaxies, and denser pockets of dark matter occur as smaller subhalos  form about individual galaxies. These have been detected by their gravity and agree fairly well with computer simulations of how dark matter should clump over the life of the Universe. A new study by researchers at the Astronomical Observatory of Bologna in Italy examined dark matter in 11 large galaxy clusters and found that there are many more or much denser subhalos than previously thought. The study analyzed the gravitational distortions of distant objects behind the galaxy clusters seen in images taken by the Hubble Space Telescope. In addition, spectroscopic measurements of star velocities were made, which can be related to the strength of gravity nearby. Astronomers are trying to understand if they need to fix something in their computer simulations of dark matter clumping, or if they do not understand some property of dark matter.

Magellanic Stream Explained – The Magellanic Stream has long been known as a huge ribbon of gas ripped off from the Large and Small Magellanic Clouds by gravitational forces from the Milky Way. But until now, computer simulations failed to explain the Stream’s mass of about a billion solar masses. Astronomers at the University of Wisconsin recently discovered that the Magellanic Clouds have a huge halo of warm gas surrounding them, and that halo supplies the quantity of gas seen in the Stream in simulations that include that halo.

Nearby Supernovas – An international team of scientists have found radioactive iron-60 in small amounts in sediments sampled from the bottom of three oceans. That iron was found only in a layer that was deposited eight million years ago and another layer that ranged from 3.2 to 1.7 million years ago. The researchers believe they were caused by the Earth passing through the remnants of supernovas that exploded nearby. They estimate that such supernovas would have occurred within 300 light-years of Earth, but not so close as to cause significant biological damage. The layer that lasted 1.5 million years would have required a series of supernovas, which could likely occur in a single aging star cluster. Both those time periods correspond to times when the Earth’s climate cooled, so that cooling could also be an effect of supernovas.

Binary Supermassive Black Holes – Quasars are powered by large amounts of matter falling into the supermassive black hole at the center of a galaxy. Because galaxies occasionally collide, there should be some quasars that have two black holes instead of one. Eventually these double black holes would likely merge, but for a time two should remain, particularly if a single accretion disk forms about the both of them. A new search by astronomers at the University of Tokyo found such a pair of black holes in a quasar. Their search looked at 35,000 known quasars using the wide-angle camera on the Subaru telescope in Hawaii. More than 400 of these merited closer examination, and only one of those was found to have a double black hole. Its components are 80 million solar masses and 200 million solar masses. Making an approximation of how many may have been missed in this study, it was estimated that about 3/10 of 1 percent of quasars have a double black hole.

Nearby Plasma Cloud – Some quasars are known that twinkle or flicker over periods of minutes. A few of those have been investigated and the flicker is caused by nearby clouds of charged particles, known as a plasma, between the Earth and the quasar. A recent investigation by an international team of astronomers led by researchers at the ASTRON Netherlands Institute for Radio Astronomy of another flickering quasar, known as J1402+5347, indicated such a plasma cloud at 0.8 light-years away, placing it within the Oort Cloud, the outermost part of our Solar System. Some of the flickering plasma clouds have been near hot stars that may have thrown off plasma, but this is clearly not the case for plasma in the Oort Cloud. Other astronomers have disputed the distance to the newly found plasma cloud and more observations of more flickering quasars are needed to fully explain them.

Strongest Magnetic Field – Observations by astronomers using Insight-HXMT, the Chinese X-ray space telescope, of a pulsar known as GRO J1008-57 show that the magnetic field strength at its surface is roughly 1 billion teslas, the strongest ever magnetic field accurately measured. Accreting matter follows the magnetic field lines down to collide with the surface of the pulsar. The observations were made during an X-ray outburst in August 2017, but the magnetic field strength was only recently calculated by the researchers from the Chinese Academy of Sciences and the Eberhard Karls University of Tübingen in Germany.

White Dwarf’s Planet – Astronomers at the University of Wisconsin-Madison discovered a Jupiter-sized exoplanet closely orbiting a white dwarf star known as WD 1856, located about 80 light-years away. In order to get to white dwarf stage of its “life,” a star passes through the red giant phase, where the star swells up and wipes out any closely-orbiting planets. The newly discovered planet must have been orbiting farther away during the star’s red giant phase, then moved closer afterward. Because it is in a triple star system, it’s possible that one of its companion stars disturbed the planet’s orbit, sending it closer to its star. What is harder to explain is how it moved closer to its star, but not so close that would be torn apart by the star’s tidal forces. The planet was found by TESS (planet finding space telescope), but has not been verified, so is technically still a planet candidate. It is about seven times the diameter of its white dwarf star, though of far less mass.

White Dwarf Density Achieved – White dwarf stars are extremely dense. They’re formed when a star roughly the mass of our Sun collapses at the end of its life down to about the size of Earth, compacting its stellar material into a small space. The density is so high that scientists have been unable to reproduce such levels in labs, until now. At Lawrence Livermore National Laboratory’s National Ignition Facility, physicists fired a burst of high intensity laser light onto a pellet of carbon and hydrogen suspended in a device known as a hohlraum. The intense energy compressed the pellet to 450 million times the pressure of our atmosphere and to 3.5 million degrees, while pummeling it with X-rays, creating a shock wave within. From this barrage, the pellet briefly attains the conditions of a white dwarf. Without actually achieving this density, scientists had only been extrapolating what the behavior might be in this condition.

Stellar Elements Versus Planets – Studies have shown that stars with low amounts of elements heavier than helium are unlikely to have exoplanets orbiting them. Planet cores form from those heavier elements left over from star formation in the form of a disk around the newborn star. A new study by the National Centre of Competence in Research PlanetS looked to see if there is further correlation between elements found in a star and the presence of planets. They hoped the spectrum of a star would indicate if it was worth spending observation time looking for possible planets orbiting it. However, no further correlation was found; stars with known planets did not have any significant difference in composition of elements. Using the Keck Telescope in Hawaii, this study looked at the spectra of 16 stars with known planets and 68 stars without. The scientists added that this may not be the final word because many exoplanets are beyond current technology to find, so the sample of stars without planets may not have been accurately chosen.