Two exoplanets spotted by NASA satellites as JWST adds its first discovery to the list

The James Webb Space Telescope has found its first exoplanet, orbiting a star 41 light years from Earth.

And while it would take just over four decades travelling at the speed of light, to reach the planet named LHS 475b it is relatively close in astronomical terms.

LHS 475b is about 1% smaller in diameter than Earth and is a rocky planet orbiting its nearest star in the Octans constellation.

The JWST is only capable of characterising the atmospheric composition of Earth-sized exoplanets (a world beyond our own solar system).

But while the John Hopkins University Applied Physics Laboratory (APL) team analysing the JWST data cannot yet able to determine whether the planet does have atmosphere, it does know some gases are not present.

“There are some terrestrial-type atmospheres that we can rule out. It can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan,” says Jacob Lustig-Yaeger from the APL.

“[And] counterintuitively, a 100% carbon dioxide atmosphere is so much more compact that it becomes very challenging to detect.”

Exoplanets are discovered regularly: 336 were discovered in 2022 between 16 and 27,000 light years from Earth.

In fact, the JWST’s exoplanet came the day after the discovery of another Earth-sized planet – this time thanks to follow-up observations by NASA’s TESS (Transiting Exoplanet Survey Satellite).

This rocky planet is the fifth to be discovered orbiting the TOI 700 red dwarf star in the Dorado constellation, about 100 light years away. It completes a lap around its star every 28 days.

Exoplanets around red dwarfs: Rocky worlds hold prospects for life away from Earth

“This is one of only a few systems with multiple, small, habitable-zone planets that we know of,” says Emily Gilbert from NASA’s Jet Propulsion Laboratory.

Artists impression of exoplanet toi 700 e orbits within the habitable zone of its star in this illustration. Its earth-size sibling, toi 700 d, can be seen in the distance.
Artists impression of exoplanet TOI 700 e orbits within the habitable zone of its star in this illustration. Its Earth-size sibling, TOI 700 d, can be seen in the distance. Credit: NASA/JPL-Caltech/Robert Hurt

“That makes the TOI 700 system an exciting prospect for additional follow up. Planet e is about 10% smaller than planet d, so the system also shows how additional TESS observations help us find smaller and smaller worlds.”

The star known as TOI 700 e also occupies its sun’s optimistic habitable zone, suggesting liquid water could exist on the planet’s surface.

This contrasts with three of its first-discovered siblings, which are too close to their star for water to liquify.

The nearby TOI 700d orbits in the star’s conservative habitable zone, which has a higher probability of both liquid water and an Earth-like atmosphere existing.

NASA hopes that continued follow-up observations of TOI 700 will lead to more exoplanet discoveries, given the addition of the e planet to the original four discovered a year ago.

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