Since its launch in December 2021, the James Webb Space Telescope (JWST) has been breaking records.
Now the instrument has spotted its first planet around a star other than our own, and with an estimated diameter equal to about 99% of the Earth it looks somewhat familiar.
Observations from NASA’s Transiting Exoplanet Survey Satellite (TESS) hinted that the planet was there, but now high-resolution imagery offered by the near-infrared spectrograph (NIRSpec) onboard JWST has confirmed it.
Despite the similarity in size, the planet is believed to be much hotter than our own world, circling a red dwarf star close enough to complete an orbit in just two days.
“There’s no question the planet is there,” says astronomer Jacob Lustig-Yaeger, of the Applied Physics Laboratory at Johns Hopkins University in Maryland. “Webb’s blank data validated it.”
This newly discovered object lies 41 light-years away in the constellation Octans and has been given the designation LHS 475 b. As with other exoplanets, it was spotted by looking at the shadow created as it passed in front of its star.
What makes the JWST special is that it can examine transmission spectra; the assortment of light wavelengths filtering around the planet that can reveal the qualities of its atmosphere.
At this time, we don’t have enough data to tell us what type of atmosphere LHS 475 b has, if any. Astronomers are so far convinced that it lacks a thick, methane-rich atmosphere like the one that shrouds Saturn’s moon Titan.
“The telescope is so sensitive and the data is so precise that we could have easily detected several different molecules, but we’re not seeing much yet,” says astrophysicist Ortiz Ceballos, from the Harvard-Smithsonian Center for Astrophysics in Massachusetts. .
But they cannot exclude a shallow atmosphere composed of pure carbon dioxide.
The extra precision offered by the JWST means that researchers can search for much smaller stars and planets. Usually, telescopes look for exoplanets larger than Jupiter, about 11 times wider than Earth.
Information is also gathered at a rapid pace: it took only two transits (or passes in front of its star) for the JWST to identify LHS 475 b and some of its characteristics. Further reading should tell us more about what we are dealing with here.
We also see the JWST producing absolutely stunning images from deep space, thanks to the sensitivity of its onboard instruments – and that’s only been going on for just over a year. There’s a lot more to come.
“These first observational results from a rocky Earth-sized planet open the door to many future possibilities for studying rocky planet atmospheres with Webb,” said Mark Clampin, director of the Astrophysics Division at the NASA headquarters in Washington, DC.
“Webb is bringing us closer and closer to a new understanding of Earth-like worlds outside our solar system, and the mission has only just begun.”
The results were presented at a gathering of the American Astronomical Society on Wednesday, January 11, 2023.