Researchers observing space with NASA’s James Webb Space Telescope have identified features of silicate clouds in the atmosphere of a distant planet. The atmosphere is constantly rising, mixing and changing throughout the 22 hours of the day, pulling warmer material up and pushing cooler material down.
The resulting changes in brightness are so dramatic that it is the most variable planetary-mass object known to date. The team, led by Brittany Miles of the University of Arizona, also detected water, methane and carbon monoxide with Webb’s data and found evidence of carbon dioxide. This is the largest number of molecules ever identified on a planet outside our solar system at the same time.
Cataloged as VHS 1256 b, the planet is about 40 light-years away and orbits two stars for a period of 10,000 years. “VHS 1256 b is about four times farther from its stars than Pluto is from our Sun, making it an excellent target for Webb,” Miles said.
“That means the planet’s light doesn’t mix with the light from its stars.” Higher up in its atmosphere, where the silicate clouds churn, temperatures reach 830 degrees Celsius (1,500 degrees Fahrenheit).
Planet VHS 1256 b is quite young, only 150 million years have passed since its formation, and it will continue to change for billions of years.
Within these clouds, Webb detected larger and smaller silicate dust grains, shown in a spectrum. “The finer silicate grains in its atmosphere may look more like tiny particles of smoke,” said co-author Beth Biller of the University of Edinburgh in Scotland. “Larger grains may be more like very hot, very small sand particles.”
VHS 1256 b has low gravity compared to more massive brown dwarfs, meaning its silicate clouds can appear and remain higher in its atmosphere, where Webb can detect them.
troubled skies
Another reason its skies are so turbulent is the planet’s age. In astronomical terms, it is quite young. Only 150 million years have passed since its formation and it will continue to change and cool for billions of years.
In many ways, the team considers these findings the first “coins” to be mined from a spectrum that researchers see as a treasure trove of data. Because they have barely begun to identify its contents.
A team from the University of Arizona used two instruments known as spectrographs aboard the James Webb Space Telescope. / NASA, ESA, CSA, J. Olmsted (STScI)
“We’ve identified the silicates, but better understanding which grain sizes and shapes correspond to which specific cloud types will require a lot of additional work,” Miles said. “This isn’t the last word on this planet: it’s the beginning of a large-scale modeling effort to fit Webb’s complex data,” he added.
While all of the features observed by the team have been detected by other telescopes on other planets in different locations in the Milky Way, the other survey teams have generally identified only one feature at a time.
“No other telescope has identified so many features at the same time for a single target,” said co-author Andrew Skemer of the University of California, Santa Cruz. “We’re seeing many molecules in a single Webb spectrum detailing this planet’s dynamic cloud and weather systems.”
While similar features have been detected on other planets, in various locations across the Milky Way, survey teams have generally identified one feature at a time.
The equipment arrived at these conclusions through the analysis of data known as spectra, compiled by two instruments on board Webb: the near infrared spectrograph (NIRSpec, by its acronym in English) and the medium infrared instrument (MIRI, by its acronym in English).
Because the planet’s orbit moves at such a great distance from its stars, the researchers were able to observe it directly, rather than using the transit technique or a coronagraph to obtain this data.
There will be much more to learn about VHS 1256 b in the coming months and years as this team and others continue to analyze Webb’s high-resolution infrared data. “There’s a lot of performance in a very modest amount of telescope time,” Biller said. “With just a few hours of observations, we have what appears to be infinite potential for further discoveries,” he added.
away from your stars
What could happen to this planet billions of years from now? Since it is so far from its stars, it will get colder over time and its skies can change from cloudy to clear.
The researchers observed VHS 1256 b as part of Webb’s First Science Observations program, designed to help transform the astronomical community’s ability to characterize planets and the disks where they form.
Because it’s so far from its stars, the planet will get colder over time, and its skies can go from cloudy to clear.
The team’s scientific paper, titled “The James Webb Space Telescope First Science Observations Program for Direct Observations of Exoplanetary Systems II: 1-20 Micron Spectrum of Planetary-Mass Companion VHS 1256-1257 b”, was published this week in The Astrophysical Journal Cards.
Finally, it should be remembered that the James Webb Space Telescope is the world’s leading space science observatory. Webb’s mission is to see beyond distant worlds around other stars and explore still enigmatic structures, as well as the origins of our universe. In this international program led by NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA) are partners.