JWST just confirmed its first exoplanet, and it’s Earth-sized: ScienceAlert

JWST just confirmed its first exoplanet, and it’s Earth-sized: ScienceAlert

JWST just confirmed its first exoplanet, and it’s Earth-sized: ScienceAlert

Since its launch in December 2021, the James Webb Space Telescope (JWST). records broken.

Now the instrument has seen its first planet around a star other than ours, and with an estimated diameter equal to about 99 percent of the Earth it looks a bit familiar.

Observations from NASA’s Transiting Exoplanet Survey Satellite (TESS) hinted that the planet was there, but now the high-resolution images from the Near-Infrared Spectrograph (NIRSpec) aboard the JWST have confirmed it.

Despite the similarity in size, the planet is believed to be much hotter than our own home world, orbiting a red dwarf star close enough to complete an orbit in just two days.

“There is no question that the planet is there,” says astronomer Jacob Lustig-Yaeger, from the Johns Hopkins University Applied Physics Laboratory in Maryland. “Webb’s pristine data validated it.”

This newly found object is located 41 light-years away in the constellation Octans and has been designated LHS 475 b. As with other exoplanets, it was spotted by looking at the shadow it formed as it passed in front of its star.

What makes the JWST special is that it can be looked at transmission spectra; the range of light wavelengths filtered around the planet that can reveal properties of its atmosphere.

JWST just confirmed its first exoplanet, and it’s Earth-sized: ScienceAlert
Readings suggest that LHS 475 b has no atmosphere dominated by methane. (NASA/ESA/CSA/L. Hustak (STScI))

For now, we don’t have enough data to tell us what kind of atmosphere LHS 475 b has, if it has one at all. Astronomers are so sure there isn’t a thick, methane-rich atmosphere like the one around Saturn’s moon Titan.

“The telescope is so sensitive and the data is so accurate that we could have easily detected several molecules, but we’re not seeing much yet,” says astrophysicist Ortiz Ceballosfrom the Harvard-Smithsonian Center for Astrophysics in Massachusetts.

But they cannot rule out that a superficial atmosphere consists of pure carbon dioxide.

The extra precision provided by the JWST means that researchers can search for stars and planets that are much smaller. Usually telescopes look for exoplanets larger than Jupiterabout 11 times wider than the Earth.

Information is also being gathered at a rapid pace: it took only two transits (or passes for its star) for the JWST to identify LHS 475 b and some of its features. Further measurements should tell us more about what we are dealing with here.

We also see that the JWST definitely produces some stunning images from deep space, thanks to the sensitivity of the onboard instruments – and it’s only been a little over a year. There’s a lot more to come.

“These first observational results of an Earth-sized rocky planet open the door to many future possibilities for studying the atmospheres of rocky planets with Webb,” says Mark Klemmingthe director of the Astrophysics Division at NASA Headquarters in Washington, DC.

“Webb is moving us ever closer to a new understanding of Earth-like worlds beyond our solar system, and the mission has only just begun.”

The findings were presented at a meeting of the American Astronomical Association on Wednesday, January 11, 2023.

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