Using NASA’s James Webb Space Telescope, scientists have confirmed for the first time an exoplanet orbiting another star. The exoplanet LHS 475 b is nearly the size of Earth and several hundred degrees warmer than Earth.
Webb also revealed that if clouds are detected on planets, it could lead to the conclusion that the planet is more like Venus, which has a carbon dioxide atmosphere and is perpetually shrouded in thick clouds. It is relatively close in the constellation of Octans at only 41 light-years away.
Scientists decided to look at the targeted planet using Webb after NASA’s Transiting Exoplanet Survey Satellite (TESS) hinted at its existence. Webb’s Near-Infrared Spectrograph (NIRSpec) easily and clearly captured the planet with just two transit observations. The fact that it is also a small, rocky planet is impressive for the observatory.
Mark Clampin, Director of the Astrophysics Division at NASA Headquarters in Washington, said: “These first observations of an Earth-sized rocky planet open the door to many future possibilities for studying the atmospheres of rocky planets with Webb. Webb brings us ever closer to a new understanding of Earth-like worlds beyond our solar system, and the mission has only just begun.”
Jacob Lustig-Yaeger of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said: “Although the team cannot conclude what is present, they can say what is not present. There are some terrestrial atmospheres we can rule out. It should not have a thick, methane-dominated atmosphere, similar to Saturn’s moon Titan.”
“There are some atmospheric compositions that have yet to be ruled out, such as a pure carbon dioxide atmosphere. Counterintuitively, an atmosphere of 100% carbon dioxide is much more dense and becomes very difficult to detect. The team needs even more precise measurements to distinguish between a pure carbon dioxide atmosphere and no atmosphere at all. We intend to obtain additional spectra this summer with upcoming observations.”
Webb’s precise light curve revealed that the planet will orbit its star within two days. Although LHS 475 b is closer to its star than any planet in our solar system, its red dwarf star has less than half the temperature of the sun, so the researchers believe it may still have an atmosphere.
Kevin Stevenson of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said: “This confirmation of a rocky planet highlights the precision of the mission’s instruments. And it is only the first of many discoveries it will make.”
Lustig-Yaeger agreed. “With this telescope, rocky exoplanets are the new frontier.”
The team’s results were presented at a press conference of the American Astronomical Society (AAS) on Wednesday, January 11, 2023.