BALTIMORE – When James Webb first dreamed of the space telescope, exoplanets had not yet been discovered. Now the observatory is showing astronomers what it can learn about planets orbiting other stars — including small ones.
Since its launch in December 2021, JWST has already extracted the atmospheres of Jupiter-sized planets already orbiting accreting stars (SN: 8/26/22). They like the more intense worlds, but not the places where astronomers hope to look for signs of life. The telescope is now getting observations of the atmospheres of exoplanets known to be of a more terrestrial persuasion, astronomers reported on December 13 and 14 in the First Science Proceedings of the JWST conference.
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And JWST is also starting to discover new world rocks.
These first peeks at worlds far away don’t yet reveal much about these remote places. But researchers are reporting that JWST’s sharpest vision in infrared wavelengths will finally be drowned out by smaller planets outside our solar system.
“The main message is, we’re in business,” said University of Montreal astronomer Björn Benneke. “We still have all the observations, but we are already quite excited.”
One of the minor planets observed by JWST is GJ 1214b, which has frustrated astronomers since its 2009 discovery.SN: 12/16/09). It is a sub-Neptune planet, meaning its size is somewhere between a rocky world like Earth and a gas like Neptune.
“What the heck are under Neptune?” asked astrologer Eliza Kempton of the University of Maryland in College Park. They could be balls of rock with a thick atmosphere of hydrogen and helium, or perhaps a watery world (SN: 2/22/12). “What we want to do with the atmospheric character is measure those atmospheres and see what it is,” Kempton said.
Astronomers have previously tried to observe the structure of GJ 1214b’s atmosphere by seeing how it filters starlight. But the air is thick and obscured, preventing astronomers from being able to detect individual molecules in it.
Instead of watching the planet pass in front of its star, Kempton and colleagues used JWST to look south of the planet before it disappeared. after a star And it worked: After 38 hours of observing, the researchers discovered an infrared planet in the south, Kempton said in a December 13 presentation.
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There is more work to be done, but initial data suggest the planet has a lot of chemical components, possibly including water and methane. Even an element heavier than hydrogen and belium enriched.
To know what kind of world GJ 1214b is, “we’re not quite there yet,” Kempton said. It could be a watery planet, he said, or a gassy planet that has lost a small amount of its light.
The telescope also had its first look at the tantalizing TRAPPIST-1 system, Benneke said in another Dec. 13 presentation (SN: 12/13/17). Discovered in 2017, the system contains seven Earth-sized worlds that are probably rocky. Three of those planets could have the right temperature for liquid water on their surface, making them particularly convenient targets for JWST and other telescopes to search for signs of life.
But TRAPPIST-1 is a small red star called an M dwarf, a type of star known for its intense flames and intense radiation. For years, astronomers debated whether the planets around these stars were hospitable to life, or whether the stars were robbing the planets of their atmospheres.SN: 6/14/17).
“If the TRAPPIST planets don’t have atmospheres, then we need to move on” from M dwarfs in the search for extraterrestrial life, says astronomer Mercedes Lόpez-Morales of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. not in the new JWST observations.
JWST’s first look at one of those potentially habitable worlds, TRAPPIST-1g, revealed no obvious signs of an atmosphere. The telescope only looked at the planet for about five hours. With more observations, the atmosphere should be revealed if it is there, Benneke said.
JWST is also getting into the planet hunting game, astronomer Kevin Stevenson said on December 14. The telescope double-checked a potentially interesting observation from another telescope and confirmed that it had seen a rocky, Earth-sized dwarf near the world. This proves that JWST can more accurately find such worlds.
“This is an exciting result, perhaps the first discovery of an exoplanet by JWST,” said Stevenson, of the Space Telescope Science Institute in Baltimore. As the planet orbits the darker star every couple of days, it’s probably around 225° Celsius on the surface – probably too hot to be habitable, he says. “Exo-Venus is more similar than exo-Earth”.
While it’s still early days for researchers, the prognosis for planet hunting using JWST is good.
The results also pave the way for future observatories, said astrophysicist John Mather of NASA’s Goddard Space Flight Center in Greenbelt, Md. Astronomers’ wish list for future missions includes a telescope that can dig even further into the details of potentially habitable worlds.
“If it’s not impossible,” Mather said, “let’s do it.”
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