Researchers observing with the NASA/ESA/Canadian Space Agency’s James Webb Space Telescope have identified features of a silicate cloud in the atmosphere of a distant planet. The atmosphere continues to rise, mix, and move 22 hours a day, warming matter and pushing cooler matter down. The resulting change in brightness is so dramatic that it is the most variable planetary object known to date. The science team also made unusually clear detections of water, methane and carbon monoxide using Webb’s data, and found evidence of carbon dioxide. This is the largest number of particles ever identified on a planet outside our solar system.
The planet, cataloged as VHS 1256 b, is located about 40 light years away and orbits not one, but two stars for 10,000 years. “VHS 1256 b is four times farther away from its star than Pluto is from our sun, making it a good target for Webb,” said a science team led by Brittany Miles of the University of Arizona. “That is, the planet’s light does not mix with the light of its stars.” Higher up in the atmosphere, where silicate clouds swirl, the temperature reaches 830 degrees Celsius.
Within the cloud, Webb detected larger and smaller silicate dust grains, which appear in the spectrum. The fine silicate grains in its atmosphere are probably more like tiny particles in smoke. Renowned co-author Beth Beller of the University of Edinburgh in England. “Large grains may be like very small, very hot particles of sand.”
VHS 1256 b has lower gravity than more massive brown dwarfs, meaning silicate clouds can arise and stay higher in its atmosphere where Webb can detect them. Another reason for the sky turbulence is the age of the planet. Astronomically, it is very small. Only 150 million years have passed since its formation – and it will continue to change and recede for billions of years.
[Image Description: Graphic titled “Exoplanet VHS 1256 b Emission Spectrum.” The label at top right reads NIRSpec and MIRI, IFU Medium-Resolution Spectroscopy. The spectrum is plotted on a graph with y- and x-axes. The graph shows jagged lines. There are labels for water, carbon monoxide, methane, and silicates.]
Credits: NASA, ESA, CSA, J. Olmsted (STScI), B. Miles (University of Arizona), S. Hinkley (University of Exeter), B. Biller (University of Edinburgh), A. Skemer (University of California, Santa Claus)
In many ways, the team considers these findings to be the first “coins” pulled from the spectrum that researchers regard as a treasure trove of data. In many ways, they are just beginning to define their content. “We have identified silicates, but a better understanding of the size and shape of the grains that correspond to certain cloud types will require a lot of additional work,” he said. says Miles. “It’s not the last word on the planet – it’s the start of a large-scale modeling effort to fit Webb’s complex data.”
Although all of the features the team observed have been seen on other planets elsewhere in the Milky Way by other telescopes, other research teams identified only one pattern at a time. “No other telescope has identified so many features simultaneously for a single target,” he said. said co-author Andrew Skimmer of the University of California, Santa Cruz. “We see many particles in a single Webb spectrum detailing dynamic clouds and weather systems on planet Earth.”
The team reached this conclusion by analyzing data known as spectra collected by two instruments aboard Webb, the near infrared spectrometer (NIRSpec) and the mid-infrared instrument (MIRI). Because planets orbit at great distances from their stars, researchers can observe them directly, rather than using transit or backbone techniques to retrieve this data.
There will be a lot to learn about VHS 1256 b in the months and years to come as the team – and others – continue to examine Webb’s high-resolution infrared data. “There’s a huge return on a very modest amount of telescope time,” he said. Biller added. “With just a few hours of observations, we have endless possibilities for additional discoveries.”
What could happen to this planet billions of years from now? Due to its great distance from the stars, it gets colder over time, and the sky can change from overcast to clear.
Researchers observed VHS 1256 b as part of Webb’s Early Release Science program, which is designed to help transform the astronomical community’s ability to distinguish planets and the disks that compose them.
Journal reference
- JWST Science Program Early Release Observations of Exoplanet Systems II: 1-to-20-micron Spectrum of Planetary-Mass Companion VHS 1256-1257 b,” will be posted on Astrophysics Journal Letter
