Read this story in Spanish here.
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 shifting during its 22-hour day, pulling hotter material up and pushing cooler material down. The resulting changes in brightness are so dramatic that it is the most variable planetary object known to date. The team, led by Brittany Miles of the University of Arizona, also made very 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 at one time.
The planet, cataloged as VHS 1256 b, is located about 40 light-years away and orbits not one, but two stars over a period of 10,000 years. “VHS 1256 b is about four times farther from its stars than Pluto is from our sun, which makes it an excellent target for Webb,” Miles said. “This means that the light from the planet is not mixed with the light from its stars.” Higher in the atmosphere, where silicate clouds ripple, temperatures reach 830 °C (1,500 °F).
Within those clouds, Webb detected larger and smaller silicate dust grains, as shown in the spectrum. “The fine silicate grains in its atmosphere may look more like tiny smoke particles,” said co-author Beth Biller, from the University of Edinburgh in Scotland. “The larger grains can be more like very small, very hot sand particles.”
VHS 1256 b has a lower gravity compared to more massive brown dwarfs, which means that silicate clouds can emerge and remain higher in its atmosphere, where Webb can detect them. Another reason why its sky is so turbulent is the age of the planet. Astronomically speaking, it is very small. Only 150 million years have passed since its formation and it will continue to change and subside for billions of years.
In many ways, the team considers these findings to be the first “coins” to be extracted from a spectrum that the researchers see as a treasure trove of data. To a large extent, they are only beginning to define their content. “We’ve identified silicates, but a better understanding of what grain sizes and shapes match specific cloud types will require a lot of additional work,” Miles said. “This is not the last word on the planet: it is the beginning of a large-scale modeling effort to fit Webb’s complex data.”
Although all of the features the team observed were detected by other telescopes on other planets at various locations in the Milky Way, other research teams have generally identified only one feature at a time. “No other telescope has identified so many features simultaneously for a single target,” said co-author Andrew Skemer of the University of California, Santa Cruz. “We see many particles, in a single web spectrum, separating the dynamic cloud and weather systems on this planet.”
The team reached these conclusions by analyzing data known as spectra, which were collected by two instruments aboard Webb: the near infrared spectrometer (NIRSpec) and the medium infrared spectrometer (MIRI). Because the planet’s orbit moves such a great distance from its stars, the researchers were able to observe it directly, rather than using a transit or para-pass technique to obtain this data.
There will be much 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 productivity in a very modest amount of telescope time,” Beller added. “With just a few hours of observations, we have what seems like an endless potential for additional discoveries.”
What could happen to this planet billions of years from now? Because it is so far from its stars, it will get colder over time and its skies may turn from cloudy to clear.
Researchers observed VHS 1256 b as part of Webb’s First Science Observations program, which is designed to help transform the astronomical community’s ability to discern planets and the disks that make them up.
The team’s scientific paper, “First Scientific Observation Program for the James Webb Space Telescope for Direct Observation of Exoplanet Systems II: 1-20-micron Spectrum of Planetary-Mass Companion VHS 1256-1257 b,” will be published in the Astrophysical Journal Letters on March 22.
The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries of our solar system, see beyond distant worlds around other stars, and explore the mysterious structures and origins of our universe and our place in it. Webb is an international program run by NASA with its partners: the European Space Agency (ESA) and the Canadian Space Agency (CSA).