James Webb Detects Methane in Temperate Exoplanet TOI199b Atmosphere

Astronomers have successfully analyzed the atmosphere of a temperate giant planet located over 330 light-years from Earth, marking a significant milestone in exoplanet research. The planet, designated TOI199b, is roughly the size of Saturn but maintains temperatures surprisingly similar to those found on Earth, estimated at around 175 degrees Fahrenheit.

This discovery, led by researchers from Pennsylvania State University and NASA’s Jet Propulsion Laboratory, was published in The Astronomical Journal. TOI199b represents a rare middle ground between the two extreme categories of giant planets commonly studied: the frigid giants like Jupiter and Saturn in our solar system, and the scorching "hot Jupiters" found orbiting very close to their stars. With an orbital period of about 100 days, it is one of only a handful of known temperate gas giants and the first of its kind to undergo detailed atmospheric analysis.

Using NASA’s James Webb Space Telescope, the team employed a technique called transmission spectroscopy. As the planet transited its star, some of the starlight passed through TOI199b's atmosphere before reaching the telescope. By analyzing this filtered light over...