James Webb Space Telescope discovers its first exoplanet

By Ashley Strickland, CNN

The James Webb Space Telescope can add another cosmic accomplishment to its list: The space observatory has been used to confirm the existence of an exoplanet for the first time.

The celestial body, known as LHS 475 b and located outside of our solar system, is almost exactly the same size as Earth. The rocky world is 41 light-years away in the Octans constellation.

Previous data collected by NASA’s Transiting Exoplanet Survey Satellite, or TESS, had suggested the planet might exist.

A team of researchers, led by staff astronomer Kevin Stevenson and postdoctoral fellow Jacob Lustig-Yaeger at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, observed the target using Webb. They watched for dips in starlight as the planet passed in front of its host star, called a transit, and watched two transits occur.

“There is no question that the planet is there. Webb’s pristine data validate it,” Lustig-Yaeger said in a statement.

The planet’s discovery was announced Wednesday at the 241st meeting of the American Astronomical Society in Seattle.

“The fact that it is also a small, rocky planet is impressive for the observatory,” Stevenson said.

Webb is the only telescope that has the capability to characterize the atmospheres of exoplanets that are the size of Earth. The research team used Webb to analyze the planet across multiple wavelengths of light to see whether it has an atmosphere. For now, the team hasn’t been able to make any definitive conclusions, but the telescope’s sensitivity picked up on a range of molecules that were present.

“There are some terrestrial-type atmospheres that we can rule out,” Lustig-Yaeger said. “It can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan.”

The astronomers will have another chance to observe the planet again over the summer and conduct follow-up analysis on the potential presence of an atmosphere.

Webb’s detections also revealed that the planet is a few hundred degrees warmer than our planet. If the researchers detect any clouds on LHS 475 b, it may turn out to be more like Venus — which is considered to be Earth’s hotter twin with a carbon dioxide atmosphere.

“We’re at the forefront of studying small, rocky exoplanets,” Lustig-Yaeger said. “We have barely begun scratching the surface of what their atmospheres might be like.”

The planet completes a single orbit around its red dwarf host star every 2 Earth days. Given that the star is less than half the temperature of our sun, it’s possible that the planet could still maintain an atmosphere despite its close proximity to the star.

The researchers believe their discovery will just be the first of many in Webb’s future.

“These first observational results from an Earth-sized, rocky planet open the door to many future possibilities for studying rocky planet atmospheres with Webb,” said Mark Clampin, Astrophysics Division director at NASA Headquarters, in a statement. “Webb is bringing us closer and closer to a new understanding of Earth-like worlds outside the Solar System, and the mission is only just getting started.”

A dusty disk

More Webb observations were shared at the meeting on Wednesday, including never-before-seen views 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 wavelegnths of light, which are invisible to the human eye.

The dusty disk around the star, named AU Mic, represents the remnants of planet formation. When small, solid objects called planetesimals — a planet in the making — crashed into each other, they left behind a big, dusty ring around the star and formed a debris disk.

“A debris disk is continuously replenished by collisions of planetesimals. By studying it, we get a unique window into the recent dynamical history of this system,” said lead study author Kellen Lawson, postdoctoral program fellow at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and member of the research team that studied AU Mic.

Webb’s capabilities allowed astronomers to see the region close to the star. Their observations and data could provide insights that aid in the search for giant planets that form wide orbits in planetary systems, not unlike Jupiter and Saturn in our solar system.

The AU Mic disk is located 32 light-years away in the Microscopium constellation. The star is about 23 million years old, so planet formation has already ceased around the star — since that process usually takes less than 10 million years, according to the researchers. Other telescopes have spotted two planets orbiting the star.

“This system is one of the very few examples of a young star, with known exoplanets, and a debris disk that is near enough and bright enough to study holistically using Webb’s uniquely powerful instruments,” said study coauthor Josh Schlieder, principal investigator for the observing program at NASA’s Goddard Space Flight Center.

The formation of stars

The Webb telescope was also used to peer inside NGC 346, a star-forming region located in a neighboring dwarf galaxy called the Small Magellanic Cloud.

About 2 billion to 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 during cosmic noon wouldn’t have one NGC 346, as the Small Magellanic Cloud does; it would have thousands,” said Margaret Meixner, an astronomer at the Universities Space Research Association and principal investigator of the research team, in a statement.

“Even if NGC 346 is now the one and only massive cluster furiously forming stars in its galaxy, it offers us a great opportunity to probe the conditions that were in place at cosmic noon.”

Observing how stars form in this galaxy allows astronomers to compare star formation in our own Milky Way galaxy.

In the new Webb image, forming stars can be seen pulling in ribbon-like gas and dust from a surrounding molecular cloud. This material feeds the formation of stars, and eventually, planets.

“We’re seeing the building blocks, not only of stars, but also potentially of planets,” said co-investigator Guido De Marchi, a space science faculty member of the European Space Agency, in a statement. “And since the Small Magellanic Cloud has a similar environment to that of galaxies during cosmic noon, it’s possible that rocky planets could have formed earlier in the history of the Universe than we might have thought.”

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