James Webb images volcanic exoplanet 30% larger

NASA’s James Webb Space Telescope has given astronomers their clearest look yet at the surface of a rocky exoplanet, according to a study published in Nature Astronomy on May 4. The planet, LHS 3844 b, is about 30% larger than Earth and orbits a red dwarf star roughly 48.5 to 49 light-years away. (cyprus-mail.com) Webb did not take a photograph in the usual sense. Instead, researchers used the telescope’s mid-infrared measurements to read heat coming from the planet’s dayside and infer what kind of rock sits at the surface. (nature.com) The result was a picture of a dark, airless and extremely hot world that researchers said looks more like Mercury or Earth’s moon than Earth. Reuters reported the findings on May 8, and institutional releases from the Max Planck Institute for Astronomy and the Center for Astrophysics | Harvard & Smithsonian identified Sebastian Zieba and Laura Kreidberg as leaders of the work. (cfa.harvard.edu) The study is notable because most previous Webb work on rocky exoplanets focused on atmospheres; this one centered on the surface itself. ### Which planet did Webb study, and where is it? LHS 3844 b is a “super-Earth,” the term astronomers use for a rocky planet larger than Earth but smaller than Neptune. (nature.com) The planet circles a star smaller and dimmer than the sun at a distance of about 49 light-years from Earth, according to Reuters and the study materials. It is also known as Kua’kua, a name cited in Reuters coverage and University of Chicago material. Its orbit is extremely tight. Reuters said the planet completes one trip around its star in about 11 hours, a configuration that leaves one hemisphere in constant daylight and the other in permanent night. (cyprus-mail.com) That geometry helped Webb isolate thermal emission from the hot dayside. ### How did Webb “see” a surface it cannot image directly? The James Webb telescope used its Mid-Infrared Instrument, or MIRI, to collect a thermal emission spectrum from 5 to 12 microns, according to the Nature paper abstract and the Harvard-Smithsonian release. Different rocks emit and absorb infrared light differently, allowing scientists to compare the observed spectrum with laboratory and model surfaces. (cyprus-mail.com) Laura Kreidberg said in the MPIA-backed material that Webb’s sensitivity made it possible to detect light coming directly from the surface of a distant rocky planet. That is why researchers described the work as a first direct surface study of this kind for a rocky exoplanet. (nature.com) ### What did the data show about the planet itself? The spectrum was best matched by a dark, low-silica surface such as basalt or other olivine-rich material, according to the Nature abstract. Reuters reported that the world appears desolate and airless, with a surface that may resemble Mercury’s. The paper also said the data ruled out some alternatives, including brighter or fresher powder-like surfaces. (arxiv.org) Temperatures on the planet are extreme. Because LHS 3844 b appears to be tidally locked, its dayside is intensely heated while the nightside remains far colder, Reuters reported. Those conditions, together with the lack of a discernible atmosphere, make it a poor candidate for habitability. (mpia.de) ### Did the study actually show active volcanism? The published study materials available in primary and institutional sources did not frame the main result as a direct detection of ongoing volcanism. The Nature abstract said the surface is consistent with dark basalt-like rock and that the measurements can inform ideas about geologic history and interior processes. EurekAlert’s summary of the research said the findings suggest LHS 3844 b may be volcanically active, but that is presented as an inference from the surface properties rather than a direct observation of eruptions. (arxiv.org) That distinction matters for how to read the result. Webb measured infrared emission from the surface and researchers compared it with modeled materials; the available primary reporting does not say the telescope saw a plume, lava flow or atmospheric volcanic gas signature. (nature.com) ### What comes next for this line of research? Sebastian Zieba and Laura Kreidberg said in the Center for Astrophysics release that surface characterization is a next step beyond atmospheric studies in understanding rocky exoplanets. University of Chicago researchers said the result could help future searches for habitable worlds by improving how scientists interpret rocky planet surfaces. (arxiv.org) Nature Astronomy published the LHS 3844 b paper on May 4, and the named teams at CfA, MPIA and collaborating institutions now have a template for applying Webb’s mid-infrared spectroscopy to other rocky worlds. Future work, as described in the study coverage, will test whether similar observations can distinguish surface composition and roughness on additional nearby exoplanets. (arxiv.org) (nature.com) (cfa.harvard.edu)