The James Webb Space Telescope confirms its first exoplanet

Exoplanet LHS 475 b and its star (illustration). Credit: ESA

Ibadan, 13 January 2023 – Researchers have confirmed the existence of an exoplanet, a planet orbiting another star, using the NASA/ESA/CSA James Webb Space Telescope for the first time. Officially classified as LHS 475 b, the planet is almost exactly the same size as Earth, reaching 99% of Earth’s diameter.

Kevin Stevenson and Jacob Lustig-Yager led the research team that made the discovery, both from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. The team chose to observe this target with Webb after carefully reviewing data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which hinted at the planet’s existence.

The Webb Near Infrared Spectrograph (NIRSpec) captured the planet easily and clearly with just two transit observations. “There is no doubt that the planet is there. Webb’s primary data confirms this,” said Lustig-Yaeger. The team tried to estimate what was in the planet’s atmosphere by analyzing its transmission spectrum. Although the data shows it is an Earth-sized terrestrial planet, they still don’t know if it has an atmosphere. While the team cannot yet conclude what is present, they are certain about what is absent.

“There are some Earth-type atmospheres that we can rule out,” Lustig-Jaeger explained. “It cannot have a dense methane-dominated atmosphere similar to Saturn’s moon Titan.” The team also notes that while the planet may not have an atmosphere, there are some atmospheric compositions we haven’t ruled out, such as an atmosphere of pure carbon dioxide.

Webb also revealed that the planet is several hundred degrees warmer than Earth. Therefore, if the researcher finds clouds, he can conclude that the planet is more like Venus. This is because the planet has an atmosphere of carbon dioxide with thick clouds constantly covering it. The researchers also confirmed that the planet completes one orbit in just two days, information that was almost instantly revealed by Webb’s precise light curve.