This artist’s concept depicts GJ 1214b, a mini-Neptune, with what is likely a steamy, hazy atmosphere. A team led by scientists with the University of Maryland and the University of Chicago used the James Webb Space Telescope to observe GJ 1214b’s atmosphere.Image courtesy of NASA/JPL-Caltech/R. Hurt

Its biggest obstacle is a thick layer of haze that covers the planet, shielding it from the prying eyes of space telescopes and hampering efforts to study its atmosphere.

Now, the James Webb Space Telescope (JWST) has solved this problem, the researchers announce in the journal Nature. The telescope’s infrared technology allows it to see objects and planetary features previously hidden by fog, clouds or space dust, aiding astronomers in their search for habitable planets and early galaxies.

A team of researchers used the JWST to observe the atmosphere of GJ 1214b by measuring the heat it emits as it orbits its host star. These results represent the first time that anyone has directly detected light emitted by a sub-Neptune exoplanet, a category of planets larger than Earth but smaller than Neptune.

Although GJ 1214b is too hot to be habitable, the researchers found that its atmosphere probably contains water vapor — possibly even in significant amounts — and is made up mostly of molecules heavier than hydrogen.

University of Maryland Associate Professor of Astronomy Eliza Kempton, lead author of the study, said their findings mark a turning point in the study of sub-Neptunian planets like GJ 1214b.

“I’ve been trying to understand GJ 1214b for more than a decade,” Kempton said in a statement. “When we received the data for this Nature paper, we were able to see light from the planet disappear as it moved behind its host star. This It has never been seen on this planet or any other of its kind, so JWST is keeping its promise,” he says.

Sub-Neptunes are the most common type of planet in the Milky Way, although none exist in our solar system. Despite the cloudiness of GJ 1214b’s atmosphere, Kempton and her co-authors determined that the planet remained their best chance of observing a sub-Neptune’s atmosphere because of its bright but small host star.

In their study, the researchers measured the infrared light emitted by GJ 1214b over the course of about 40 hours, the time it takes for the planet to orbit its star. As day turns to night, the amount of heat that travels from one side of the planet to the other depends largely on the composition of its atmosphere. This research method, known as phase curve observation, opened a new window into the planet’s atmosphere.

“JWST operates with longer wavelengths of light than previous observatories, which gives us access to the heat emitted by the planet and allows us to create a map of the planet’s temperature,” Kempton explains. “We have finally been able to see GJ 1214b in a new light”.

By measuring movement and heat fluctuation, the researchers determined that GJ 1214b does not have a hydrogen-dominated atmosphere.

The question of whether GJ 1214b contains water has long interested astronomers. Earlier observations by NASA’s Hubble Space Telescope suggested that GJ 1214b could be a waterworld, a loose term for any planet that contains a significant amount of water.

The latest data from the JWST revealed trace amounts of water, methane, or some mixture of both. These substances match a subtle absorption of light observed in the range of wavelengths observed by JWST. More study will be needed to determine the exact composition of the planet’s atmosphere, but Kempton notes that the evidence remains consistent with the possibility of large amounts of water.

“GJ 1214b, based on our observations, could be a water world,” Kempton said. “We think we detected water vapor, but it’s challenging because water vapor absorption overlaps with methane absorption, so we don’t “We can say 100% that we detected water vapor and not methane. However, we see this evidence in both hemispheres of the planet, which increases our confidence that there is indeed water there.”

The researchers made another surprising discovery in their study: GJ 1214b is incredibly reflective. The planet was not as hot as expected, indicating to the researchers that something in the atmosphere is reflecting the light.

According to Kempton, there is plenty of scope for follow-up studies, including those that take a closer look at the high-altitude aerosols that form the haze — or possibly clouds — in GJ 1214b’s atmosphere. Previously, researchers thought it could be a dark, soot-like substance that absorbs light. However, the discovery that the exoplanet is reflective raises new questions.

source: https://www.nature.com/articles/s41586-023-06159-5