The swirling clouds detected by the James Webb Space Telescope in the atmosphere of exoplanet VHS 1256 b are depicted in this illustration. VHS 1256 b is located approximately 40 light-years away and is in orbit around two stars that are tightly rotating around each other. The silicate dust-filled clouds on the planet continuously rise, mix, and move during its 22-hour day.
Credits: NASA, ESA, CSA, J. Olmsted (STScI)
March 19, 2023
Silicate cloud structures in the atmosphere of a distant planet have been identified by scientists using the NASA/ESA/CSA James Webb Space Telescope to observe. Throughout its 22-hour day, the atmosphere is continuously rising, blending, and flowing, pushing colder stuff downward and pulling warmer material above. It is the most changeable planetary-mass object to date because the accompanying brightness variations are so abrupt. Using Webb's data, the scientists team also produced remarkably precise detections of water, methane, and carbon monoxide and discovered indications of carbon dioxide. This is the most molecules that have ever been discovered at once on a planet outside of our Solar System.
The planet, designated VHS 1256 b, orbits not one, but two stars during a 10,000-year period and is located around 40 light-years away. VHS 1256 b is a wonderful target for Webb since it is nearly four times as far from its stars as Pluto is from the Sun, according to science team leader Brittany Miles of the University of Arizona. That indicates that the planet's light is not diluted by that of its stars. Temperatures rise to an oppressive 830 degrees Celsius higher in its atmosphere, where the silicate clouds are roiling.
Webb discovered silicate dust particles of various sizes within those clouds, which are displayed on a spectrum. The co-author Beth Biller of the University of Edinburgh in the United Kingdom highlighted that the atmosphere's finer silicate grains may resemble small particles in smoke. "The larger grains might be more like very hot, very small sand particles."
In contrast to more massive brown dwarfs, VHS 1256 b has a low gravity, which allows its silicate clouds to form and persist higher in its atmosphere where Webb can detect them. The age of the planet is another factor contributing to its tumultuous sky. It's rather new in astronomical terms. It created only 150 million years ago, and over the course of many billions of years, it will continue to alter and cool.
The team sees these results as the first "coins" discovered in a field that is thought to contain a wealth of information. They've really only just started to figure out what it contains. We've found silicates, but further research is necessary to determine which grain sizes and shapes correspond to different kinds of clouds, according to Miles. This is just the start of a massive modeling effort to match Webb's complex data; it's not the last word on this planet.
Other study teams often detected only one feature at a time, even if all of the features the team witnessed have been discovered on other planets elsewhere in the Milky Way by other observatories. No other telescope, according to co-author Andrew Skemer of the University of California, Santa Cruz, "has found so many features at once for a single object." The dynamic cloud and weather systems of the globe are being revealed by a large number of molecules in a single spectrum from Webb.
The Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument, two instruments on board Webb, collected data known as spectra that the scientists then used to draw these conclusions (MIRI). Instead of employing the transit technique or a coronagraph to collect this data, the researchers were able to study the planet directly because it orbits its stars at such a considerable distance from one another.
In the next months and years, as this team and others continue to sort through Webb's high-resolution infrared data, there will be a ton more to learn about VHS 1256 b.
As part of Webb's Early Release Science initiative, which aims to revolutionize the scientific community's ability to characterize planets and the discs from which they emerge, the researchers discovered VHS 1256 b.