MARYLAND — Exoplanets weren’t even known when the James Webb Space Telescope was first conceived. The observatory is currently demonstrating to astronomers what it has discovered about planets orbiting other stars, even the smaller ones.
JWST had already “sniffed” the atmospheres of Jupiter-sized planets circling searingly close to their stars since its launch in December 2021 (SN: 8/26/22). These powerful worlds are fascinating, but they are not the locations where astronomers hope to search for life. Astronomers revealed December 13 and 14 at the First Science Results from JWST meeting that the telescope is already catching glimpses of atmospheres on known exoplanets of the more earthly variety.
These first glimpses of other planets don’t yet disclose anything about these far-off places. However, scientists are encouraged by what JWST’s keen infrared vision may ultimately reveal about the smaller planets outside of our solar system.
Astronomer Björn Benneke from the University of Montreal said, “The main message is, we’re in business.” Even though not all of the observations are in yet, they are already very interesting.
GJ 1214b is one of the minor planets that JWST examined. Since its discovery in 2009 (SN: 12/16/09), astronomers have been baffled by this planet. Its size is between that of a solid planet like Earth and a gaseous planet like Neptune, making it a sub-Neptune.
Sub-Neptunes: What the heck are they? Asking University of Maryland at College Park astronomer Eliza Kempton. They might be water worlds or rocky balls with dense hydrogen and helium atmospheres (SN: 2/22/12). With atmospheric characterization, Kempton explained, “what we’d like to do is measure their atmospheres and see which is which.”
Astronomers previously attempted to determine the composition of GJ 1214b’s atmosphere by observing the way starlight was refracted across it. However, because of how dense and cloudy the atmosphere is, astronomers are unable to identify specific chemicals within it.
Kempton and colleagues utilized JWST to search for the planet’s brightness just before it vanished behind the star rather than watching the planet pass in front of its star. And it succeeded: According to Kempton in a presentation on December 13, the astronomers discovered the planet’s infrared glow after 38 hours of observation.
Although there is still work to be done, preliminary findings indicate the planet contains many chemical elements, maybe including water and methane. Additionally, it is abundant in elements heavier than helium and hydrogen.
Kempton added that when it comes to understanding the nature of GJ 1214b, “I’d say we’re not quite there yet.” She speculated that it might be a watery planet or a gaseous planet that has lost a significant amount of its lighter elements.
Benneke stated in a different presentation on December 13 that the telescope also got its first glimpse of the intriguing TRAPPIST-1 system (SN: 12/13/17). The plan, which was founded in 2017, has seven Earth-sized, likely rocky worlds. For JWST and other observatories to search for signs of life, three of those planets are very intriguing targets because they may have the correct temperatures for liquid water to exist on their surfaces.
However, TRAPPIST-1 is a tiny, red star known as an M dwarf, a kind of star infamous for ferocious outbursts and powerful radiation. Astronomers have argued for years about whether life could exist on planets orbiting these stars or whether these planets’ atmospheres would be destroyed by the stars (SN: 6/14/17).
In the hunt for extraterrestrial life, astronomer Mercedes Lpez-Morales of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who was not involved in the new JWST observations, states that “if the TRAPPIST planets don’t have atmospheres, then we need to move on” from M dwarfs.
JWST’s first look at one of those potentially habitable worlds, TRAPPIST-1g, did not reveal any clear signs of an atmosphere. But the telescope looked at the planet for only about five hours. With more observations, an atmosphere should be detectable if it’s there, Benneke said.
Astronomer Kevin Stevenson announced on December 14 that JWST is also entering the planet-hunting game. The telescope confirmed that it had observed a rocky, Earth-sized globe surrounding a nearby M dwarf after verifying an observation from another telescope that might have been intriguing. This demonstrates that JWST has the accuracy needed to locate such worlds.
Possibly the first exoplanet discovered by JWST, it is a thrilling result, according to Stevenson of the Space Telescope Science Institute in Baltimore. He estimates that the planet’s surface temperature is roughly 225° Celsius, which is probably too hot to be habitable because it rounds its faint star every two days. It resembles an exo-Venus rather than an exo-Earth.
Despite the fact that it is still early, the researchers stressed that the outlook for planet searching with JWST is promising.
According to astrophysicist John Mather of the NASA Goddard Space Flight Center in Greenbelt, Maryland, the findings are also paving the way for future observatories. The addition of a telescope that can delve even further into the specifics of potentially habitable worlds is on the wish list of astronomers for upcoming missions.
