It's no small matter to add 301 newly validated planets to an exoplanet tally already totalling 4,569. But it's even more interesting to learn that the new planets are drawn out of previously collected data, as analyzed by a deep neural network. The 'classifier' in question is called ExoMiner, describing machine learning methods that learn by examining large amounts of data. With the help of the NASA supercomputer called Pleiades, ExoMiner seems to be a wizard at separating actual planetary signatures from the false positives that plague researchers. ExoMiner is described in a paper slated for The Astrophysical Journal, where the results of an experimental study are presented, using data from the Kepler and K2 missions. The data give the machine learning tools plenty to work with, considering that Kepler observed 112,046 stars in its 115-degree square search field, identifying over 4000 candidates. More than 2300 of these have been confirmed. The Kepler extended mission K2 detected...

Discovered in 1915, Proxima Centauri has been a subject of considerable interest ever since, as you would expect of the star nearest to our own. But I had no idea research into planets around Proxima went all the way back to the 1930s. Nonetheless, a new paper from Emily Gilbert (University of Chicago) and colleagues mentions a 1938 attempt by Swedish astronomer Erik Holmberg to use astrometric methods to search for one or more Proxima planets. The abstract of the Holmberg paper (citation below) reads in part: Many parallax stars show periodic displacements. These effects probably are to be explained as perturbations caused by invisible companions. Since the amplitudes of the orbital motion are very small, the masses of the companions will generally be very small, too. Thus Proxima Centauri probably has a companion, the mass of which is only some few times larger than the mass of Jupiter. A preliminary investigation gives the result that 25% of the total number of parallax stars may...

We talked about the TOLIMAN mission last April, and the renewed interest in astrometry as the key to ferreting out possible planets around Alpha Centauri A and B. I was fortunate enough to hear Peter Tuthill (University of Sydney), who leads the team that has been developing the concept, rough out the idea at Breakthrough Discuss five years ago; Céline Bœhm (likewise at the University of Sydney) reported on more recent work at the virtual Breakthrough Discuss session this past spring. We now have an announcement from scientists involved that the space telescope mission will proceed. Eduardo Bendek (JPL) is a member of the TOLIMAN team: "Even for the very nearest bright stars in the night sky, finding planets is a huge technological challenge. Our TOLIMAN mission will launch a custom-designed space telescope that makes extremely fine measurements of the position of the star in the sky. If there is a planet orbiting the star, it will tug on the star betraying a tiny, but...

Circumbinary planets are those that orbit two stars, a small but growing category of worlds -- we've detected some 14 thus far, thanks to Kepler's good work, and that of the Transiting Exoplanet Survey Satellite (TESS). The latest entry, TIC 172900988, illustrates the particular challenge such planets represent. Transit photometry is a standard method for finding planets, detecting the now familiar drop in starlight as the planet moves between us and the surface of the host star. Kepler found thousands of exoplanets this way. But when two stars are involved, things get complicated. Image: The newly discovered planet, TIC 172900988b, is roughly the radius of Jupiter, and several times more massive, but it orbits its two stars in less than one year. This world is hot and unlike anything in our Solar System. Credit: PSI/Pamela L. Gay. Three transits are required to determine the orbital path of a planet. For us to make a detection, a circumbinary planet will have to transit both stars,...

Although we’ve been talking this week about big telescopes, from extremely large designs like the Thirty Meter Telescope and the European Extremely Large Telescope to the space-based HabEx/LUVOIR descendant prioritized by Astro2020, small instruments continue to do interesting work around the edges. I just noticed a tiny one called the Star-Planet Activity Research CubeSat (SPARCS) that fills a gap in our study of M-dwarfs, those small stars whose flares are so problematic for habitability. Under development at Arizona State University, the space-based SPARCS is just halfway into its development phase, but let’s take a look at it in light of ongoing work on M-dwarf planets, because it bodes well for turning theories about flare activity into data that can firm up our understanding. The problem is that while theoretical studies delve into ultraviolet flaring on these stars, the longest intensive UV monitoring on an M-dwarf done thus far has been a thirty hour effort with the Hubble...

The surge of interest in white dwarfs continues. We've known for some time that these remnants of stars like the Sun, having been through the red giant phase and finally collapsing into a core about the size of the Earth, can reveal a great deal about objects that have fallen into them. That would be rocky material from planetary objects that once orbited the star, just as the planets of our Solar System orbit the Sun in our halcyon, pre-red-giant era. The study of atmospheric pollution in white dwarfs rests on the fact that white dwarfs that have cooled below 25,000 K have atmospheres of pure hydrogen or helium. Heavier elements sink rapidly to the stellar core at these temperatures, so the only source of elements higher than helium -- metals in astronomy parlance -- is through accretion of orbiting materials that cross the Roche limit and fall into the atmosphere. These contaminants of stellar atmospheres are now the subject of a new investigation led by astronomer Siyi Xu (NSF...

The idea that the composition of a star and its rocky planets are connected is a natural one. Both classes of object accrete material within a surrounding gas and dust environment, and thus we would expect a link between the two. Testing the hypothesis, researchers from three institutions -- the Instituto de Astrofísica e Ciências do Espaço (Portugal), the NCCR PlanetS project at the University of Bern, and the University of Zürich -- have confirmed the concept while fine-tuning the details. After all, we still have to explain iron-rich Mercury as an outlier in our own Solar System. Image: Mercury has an average density of 5430 kilograms per cubic meter, which is second only to Earth among all the planets. It is estimated that the planet Mercury, like Earth, has a ferrous core with a size equivalent to two-thirds to three-fourths that of the planet's overall radius. The core is believed to be composed of an iron-nickel alloy covered by a mantle and surface crust. Credit: NASA....

A gas giant similar to Jupiter, and with a somewhat similar orbit, revolves around a white dwarf located about 6500 light years out toward galactic center. As reported in a paper in Nature, this is an interesting finding because stars like the Sun eventually wind up as white dwarfs, so we have to wonder what kind of planets could survive a star’s red giant phase and continue to orbit the primary. If Earth one day is engulfed, will the gas giants survive? The new discovery implies that result, and marks the first confirmed planetary system that looks like what ours could become. Image: An artist’s rendition of a newly discovered Jupiter-like exoplanet orbiting a white dwarf. This system is evidence that planets can survive their host star’s explosive red giant phase, and is the first confirmed planetary system that serves as an analogue to the face of the Sun and Jupiter in our own Solar System. Credit: W. M. Keck Observatory/Adam Makarenko. Underlining just how faint white dwarfs are...