The planets orbiting the young star TOI 451 should be useful for astronomers working on the evolution of atmospheres on young planets. This is a TESS find, three planets tracked through their transits and backed by observations from the now retired Spitzer Space Telescope, with follow-ups as well from Las Cumbres and the Perth Exoplanet Survey Telescope. TOI 451 (also known as CD-38 1467) is about 400 light years out in Eridanus, a star with 95% of the Sun's mass, some 12% smaller and rotating every 5.1 days. That rotation is interesting, as it's more than five times faster than our Sun rotates, a marker for a young star, and indeed, astronomers have ways of verifying that the star is only about 120 million years old. Here the Pisces-Eridanus stream, only discovered in 2019, becomes a helpful factor. A stream of stars forms out of gravitational interactions between our galaxy and a star cluster or dwarf galaxy, shoe-horning stars out of their original orbit to form an elongated flow....

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...