James Webb Space Telescope finds its first exoplanet
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The James Webb Space Telescope can add another cosmic achievement to its list: the space observatory has been used for the first time to confirm the existence of an exoplanet.
The celestial body, known as LHS 475 b and located outside our solar system, is almost exactly the same size as Earth. The rocky world is 41 light-years away in the constellation of Octans.
Previous data collected by NASA’s Transiting Exoplanet Survey Satellite, or TESS, had suggested the planet might exist.
A team of researchers, led by employees astronomer Kevin Stevenson and postdoctoral researcher Jacob Lustig-Yaeger at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, observed the target using Webb. They watched dips in the starlight as the planet passed in front of its host star, called a transit, and saw two transits take place.
“There is no question that the planet is there. Webb’s pristine data validates it,” Lustig-Yaeger said in a statement.
The discovery of the planet was announced Wednesday at the 241st meeting of the American Astronomical Society in Seattle.
“The fact that it’s also a small, rocky planet is impressive for the observatory,” Stevenson said.
Webb is the only telescope capable of characterizing the atmospheres of exoplanets the size of Earth. The research team used Webb to analyze the planet across multiple wavelengths of light to see if it has an atmosphere. For now, the team hasn’t been able to draw any firm conclusions, but the telescope’s sensitivity picked up a range of molecules present.
“There are some terrestrial atmospheres we can rule out,” Lustig-Yaeger said. “It should not have a thick, methane-dominated atmosphere similar to that of Saturn’s moon Titan.”
The astronomers will have another chance in the summer to observe the planet again and conduct follow-up analyzes for the possible presence of an atmosphere.
Webb’s detections also revealed that the planet is several hundred degrees warmer than our planet. If the researchers detect clouds on LHS 475 b, it may turn out to be more like Venus — which is considered Earth’s hotter twin with a carbon dioxide atmosphere.
“We are at the forefront of studying small, rocky exoplanets,” said Lustig-Yaeger. “We’re just beginning to scratch the surface of what their atmospheres might look like.”
The planet completes a single orbit around its red dwarf star every 2 Earth days. Since the star has less than half the temperature of our sun, it’s possible that the planet could still maintain an atmosphere despite its proximity to the star.
The researchers believe their discovery will be just the first of many in Webb’s future.
“These first observational results of an Earth-sized rocky planet open the door to many future possibilities for studying the atmospheres of rocky planets with Webb,” Mark Clampin, director of the Astrophysics Division at NASA Headquarters, said in a statement. “Webb is moving us ever closer to a new understanding of Earth-like worlds beyond the solar system, and the mission has only just begun.”
More Webb observations were shared at Wednesday’s meeting, including never-before-seen images of a dusty disk swirling around a nearby red dwarf star.
The telescope’s images mark the first time such a disk has been captured in these infrared wavelengths of light, which are invisible to the human eye.
The dusty disk around the star, called AU Mic, represents the remnants of planet formation. When small, solid objects called planetesimals — a planet in the making — collided, they left a large, dusty ring around the star and formed a debris disk.
“A debris disk is continuously replenished by planetesimal collisions. Studying it gives us a unique insight into the recent dynamical history of this system,” said lead study author Kellen Lawson, a postdoctoral program officer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a member of the research team that studied AU Mic.
Webb’s capabilities allowed astronomers to see the area close to the star. Their observations and data could provide insights that help search for giant planets that form broad orbits in planetary systems, similar to Jupiter and Saturn in our solar system.
The AU Mic disk is located 32 light-years away in the constellation Microscopium. The star is about 23 million years old, so the formation of planets around the star has already stopped – since that process usually takes less than 10 million years, according to the researchers. Other telescopes have discovered two planets orbiting the star.
“This system is one of the few examples of a young star, with known exoplanets, and a debris disk close enough and bright enough to study holistically using Webb’s uniquely powerful instruments,” said co-author Josh Schlieder, principal investigator of the observational program at NASA’s Goddard Space Flight Center.
The Webb telescope was also used to look into NGC 346, a star-forming region in a neighboring dwarf galaxy called the Small Magellanic Cloud.
About 2 billion until 3 billion years after the big bang that created the universe, galaxies were filled with fireworks of star formation. This peak of star formation is called “cosmic noon”.
“A galaxy at cosmic noon would not have one NGC 346 like the Small Magellanic Cloud; it would have thousands,” said Margaret Meixner, an astronomer with the Universities Space Research Association and principal investigator on the research team, in a statement.
“Even if NGC 346 is now the only truly massive cluster furiously forming stars in its galaxy, it gives us a great opportunity to explore the conditions that existed on cosmic noon.”
By observing how stars form in this galaxy, astronomers can compare star formation in our own Milky Way galaxy.
In the new Webb image, emerging stars can be seen pulling in ribbon-like gas and dust from a surrounding molecular cloud. This material fuels the formation of stars and eventually planets.
“We are seeing the building blocks, not just of stars, but possibly of planets,” co-researcher Guido De Marchi, a European Space Agency faculty member of space sciences, said in a statement. “And since the Small Magellanic Cloud has a similar environment to galaxies during cosmic noon, it’s possible that rocky planets formed earlier in the universe’s history than we might have thought.”
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