We may or may not have imaged a planet around Alpha Centauri A, possibly a ‘warm Neptune’ at an orbital distance of roughly 1 AU, the distance between Earth and the Sun. Let’s quickly move to the caveat: This finding is not a verified planet, and may in fact be an exozodiacal disk detection or even a glitch within the equipment used to see it. But as the paper notes, the finding called C1 is “is not a known systematic artifact, and is consistent with being either a Neptune-to-Saturn-sized planet or an exozodiacal dust disk.“ So this is interesting. As it may be some time before we can make the call on C1, I want to emphasize the importance not so much of the possible planet but the method used to investigate it. For what the team behind a new paper in Nature Communications has revealed is a system for imaging in the mid-infrared, coupled with long observing times that can extend the capabilities of ground-based telescopes to capture planets in the habitable zone of other nearby...

Although it seems so long ago as to have been in another century (which it actually almost was), the first detection of an exoplanet atmosphere came in the discovery of sodium during a transit of the hot Jupiter HD 209458b in 2002. To achieve it, researchers led by David Charbonneau used the method called transmission spectroscopy, in which they analyzed light from the star as it passed through the atmosphere of the planet. Since then, numerous other compounds have been found in planetary atmospheres, including water, methane and carbon dioxide. Scientists also expect to find the absorption signatures of metallic compounds in hot Jupiters, and these have been detected in brown dwarfs as well as ultra-hot Jupiters. Now we have new work out of SRON Netherlands Institute for Space Research and the University of Groningen. Led by Marrick Braam, a team of astronomers has found evidence for chromium hydride (CrH) in the atmosphere of the planet WASP-31b, a hot Jupiter with a temperature of...

'Xallarap' is parallax spelled backward (at least it's not another acronym). And while I doubt the word will catch on in common parlance, the effect it stands for is going to be useful indeed for astronomers using the Nancy Grace Roman Space Telescope. This is WFIRST -- the Wide Field Infrared Survey Telescope -- under its new name, a fact I mention because I think this is the first time we've talked about the mission since the name change in 2020. Image: High-resolution illustration of the Roman spacecraft against a starry background. Credit: NASA's Goddard Space Flight Center. While a large part of its primary mission will be devoted to dark energy and the growth of structure in the cosmos, a significant part of the effort will be directed toward gravitational microlensing, which should uncover thousands of exoplanets. This is where the xallarap effect comes in. It's a way of drawing new data out of a microlensed event, so that while we can continue to observe planets around a...

A planet like GJ 3512 b is hard to explain. Here we have a gas giant that seems to be the result of gravitational instabilities inside the ring of gas and dust that circles its star. This Jupiter-like world is unusual because of the ratio between planet and star. The Sun, for example, is about 1050 times more massive than Jupiter. But for GJ 3512 b, that ratio is 270, a reflection of the fact that this gas giant orbits a red dwarf with about 12 percent of the Sun’s mass. How does a red dwarf produce a debris disk that allows such a massive planet to grow? Image: Comparison of GJ 3512 to the Solar System and other nearby red-dwarf planetary systems. Planets around solar-mass stars can grow until they start accreting gas and become giant planets such as Jupiter, in a few millions of years. However, up to now astronomers suspected that, except for some rare exceptions, small stars such as Proxima, TRAPPIST-1, Teegarden’s star, and GJ 3512 were not able to form Jupiter mass planets....

Yesterday's story on the seven planets around TRAPPIST-1 dovetails nicely with the just announced find from scientists at CHEOPS. The ESA space telescope has determined that there are six planets around the star TOI-178. About 200 light years from Earth, this is a high proper-motion K-dwarf, the outer five of whose planets are locked into a 2:4:6:9:12 chain of Laplace resonances. The innermost world does not participate in the resonance. Image: Infographic of the TOI-178 planetary system. Credit: ESA. But more to the point of the TRAPPIST-1 comparison, whereas the seven planets there show similar densities, implying like compositions, the six worlds around TOI-178 show, in complete contrast to the orderly harmonics of their orbits, a wide range in density. The two inner planets have densities compatible with rocky worlds, while the outer four are gaseous. This is unusual for systems in this kind of complex resonance. No wonder ESA project scientist Kate Isaak is drawn up short: "It...

Image: Artist's depiction of the TRAPPIST-1 star and its seven worlds. Credit: NASA/JPL-Caltech/R. Hurt (IPAC). As if we needed another indication that the TRAPPIST-1 system is utterly different from our own, consider new work led by Eric Agol (University of Washington), which examines this seven-planet system in terms of the planets' density. The planets here are all similar in size to Earth. Compare that with the huge range in planetary size we see in our own system. The new work tightens orbital dynamics and calculates their densities, showing they are all about 8 percent less dense than the rocky planets around Sol. In the paper, the TRAPPIST-1 densities are calculated through analysis of abundant data (over 1,000 hours of observation by Spitzer alone, along with significant contributions from Kepler and ground-based telescopes like TRAPPIST and SPECULOOS). They are refined through computer simulations on planetary orbits, showing a system where planetary composition begs for an...

TESS, our Transiting Exoplanet Survey Satellite, continues to roll up interesting planet candidates, with over 2450 TESS Objects of Interest (TOI) thus far identified. The one that catches my eye this morning showed up in the lightcurve of TOI-1259A, a K-dwarf some 385 light years away. The planet designated TOI-1259Ab is Jupiter-sized but some 56 percent less massive, with a 3.48 day orbit at 0.04 AU, and an equilibrium temperature of 963 K. This system gets interesting, though, not so much for the planet but the other star, a white dwarf (TOI-1259B) in a wide orbit at 1648 AU from the K-dwarf. A team of astronomers led by David Martin (Ohio State University) finds an effective temperature of 6300 K, a radius of 0.013 solar radii and a mass of 0.56 solar masses, a set of characteristics that allow the team to estimate that the system is just over 4 billion years old. Image: SDSS image of the planet host TOI-1259A and its bound white dwarf companion TOI-1259B. Credit: Martin et al.,...

The Kepler mission produced so much data -- 2394 exoplanets, 2366 candidates by the end of spacecraft operations in 2018 -- that we might forget how quickly all this came about. The first Kepler results started being announced in 2010. One of these, the second candidate to emerge, was KOI-5Ab, which was a tough pick in the early going given its position within a triple star system. An ambiguous detection, it was soon left behind, its status uncertain, as the numbers of more definitive candidates swelled. Caltech's David Ciardi, who discussed this elusive system at the recent virtual meeting of the American Astronomical Society, says this about it: "KOI-5Ab got abandoned because it was complicated, and we had thousands of candidates. There were easier pickings than KOI-5Ab, and we were learning something new from Kepler every day, so that KOI-5 was mostly forgotten." Ciardi, who is chief scientist at NASA's Exoplanet Science Institute, has now pulled KOI-5Ab back to vibrant life....