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Researchers observing with NASA’s James
Webb Space Telescope have pinpointed silicate cloud features in a distant
planet’s atmosphere. The atmosphere is constantly rising, mixing, and moving
during its 22-hour day, bringing hotter material up and pushing colder material
down. The resulting brightness changes 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 made extraordinarily clear detections of
water, methane and carbon monoxide with Webb’s data, and found evidence of
carbon dioxide. This is the largest number of molecules ever identified all at
once on a planet outside our solar system.
Cataloged as VHS 1256 b, the planet is
about 40 light-years away and orbits not one, but two stars over a 10,000-year
period. “VHS 1256 b is about four times farther from its stars than Pluto is
from our Sun, 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
atmosphere, where the silicate clouds are churning, temperatures reach a
scorching 1,500 degrees Fahrenheit (830 degrees Celsius).
This 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. Its clouds, which are filled with silicate dust, are constantly rising, mixing, and moving during its 22-hour day. Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)
Within those clouds, Webb detected
both larger and smaller silicate dust grains, which are shown on a spectrum. “The finer silicate grains in its
atmosphere may be more like tiny particles in smoke,” noted co-author Beth
Biller of the University of Edinburgh in Scotland. “The larger
grains might be more like very hot, very small sand particles.”
VHS 1256 b has low gravity compared
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 reason 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
researchers view as a treasure chest of data. In many ways, they’ve only begun
identifying its contents. “We’ve identified silicates, but better understanding
which grain sizes and shapes match specific types of clouds is going to take a
lot of additional 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 complex
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 identified only one at a time.
“No other telescope has identified so many features at once for a single
target,” said co-author Andrew Skemer 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 dynamic cloud and weather systems.”
A research team led by Brittany
Miles of the University of Arizona used two instruments known as spectrographs
aboard the James Webb Space Telescope, one on its Near Infrared Spectrograph
(NIRSpec) and another on its Mid-Infrared Instrument (MIRI) to observe a vast
section of near- to mid-infrared light emitted by planet VHS 1256 b. They
plotted the light on the spectrum, identifying signatures of silicate clouds,
water, methane and carbon monoxide. They also found evidence of carbon dioxide.
Credits: Image: NASA, ESA, CSA, J. Olmsted (STScI); Science: Brittany
Miles (University of Arizona), Sasha Hinkley (University of Exeter), Beth
Biller (University of Edinburgh), Andrew Skemer (University of California,
Santa Cruz)
The team came to these conclusions
by analyzing data known as spectra 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
researchers were able to observe it directly, rather than using the transit technique or a coronagraph to take this 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 community’s ability to characterize
planets and the disks where they form.
The team's paper, entitled “The
JWST Early Release Science Program for Direct Observations of Exoplanetary
Systems II: A 1 to 20 Micron Spectrum of the 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 in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Source: NASA’s Webb Spots Swirling, Gritty Clouds on Remote Planet | NASA
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