Free Astronomy Magazine May-June 2023

31 MAY-JUNE 2023 ASTRO PUBLISHING which makes it a great target for Webb,” Miles said. “That means the planet’s light is not mixed with light from its stars.” Higher up in its at- mosphere, where the silicate clouds are churning, temperatures reach a scorching 1,500 degrees Fahrenheit (830 degrees Celsius). Within those clouds, Webb detected both larger and smaller silicate dust grains, which are shown on a spec- trum. “The finer silicate grains in its atmosphere may be more like tiny particles in smoke,” noted co-author Beth Biller of the University of Edin- burgh in Scotland. “The larger grains might be more like very hot, very small sand particles.” VHS 1256 b has low gravity com- pared to more massive brown dwarfs, which means that its silicate clouds can appear and remain higher in its atmosphere where Webb can detect them. Another rea- son its skies are so turbulent is the planet’s age. In astronomical terms, it’s quite young. Only 150 million years have passed since it formed – and it will continue to change and cool over billions of years. In many ways, the team considers these findings to be the first “coins” pulled out of a spectrum that re- searchers view as a treasure chest of data. In many ways, they’ve only begun identifying its contents. “We’ve identified silicates, but bet- ter understanding which grain sizes and shapes match specific types of clouds is going to take a lot of ad- ditional work,” Miles said. “This is not the final word on this planet – it is the beginning of a large-scale modeling effort to fit Webb’s com- plex data.” Although all of the features the team observed have been spotted on other planets elsewhere in the Milky Way by other telescopes, other research teams typically iden- tified only one at a time. “No other telescope has identified so many features at once for a single tar- get,” said co-author Andrew Ske- mer of the University of California, Santa Cruz. “We’re seeing a lot of molecules in a single spectrum from Webb that detail the planet’s dy- namic cloud and weather systems.” The team came to these conclusions by analyzing data known as spec- tra gathered by two instruments aboard Webb, the Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI). Since the planet orbits at such a great distance from its stars, the re- searchers were able to observe it di- rectly, rather than using the transit technique or a coronagraph to take these data. There will be plenty more to learn about VHS 1256 b in the months and years to come as this team – and others – continue to sift through Webb’s high-resolution infrared data. “There’s a huge return on a very modest amount of telescope time,” Biller added. “With only a few hours of observations, we have what feels like unending potential for additional discoveries.” What might become of this planet billions of years from now? Since it’s so far from its stars, it will become colder over time, and its skies may transition from cloudy to clear. The researchers observed VHS 1256 b as part of Webb’s Early Release Science program, which is designed to help transform the astronomical commu- nity’s ability to characterize planets and the disks where they form. T his illustration conceptualizes the swirling clouds identified by the James Webb Space Telescope in the atmosphere of exoplanet VHS 1256 b. The planet is about 40 light-years away and orbits two stars that are locked in their own tight rotation. [NASA, ESA, CSA, Joseph Olmsted (STScI)] !