LHS 475 b
First exoplanet confirmed by the James Webb Space Telescope.
LHS 475 b is a rocky planet about 40.7 light-years from Earth, located in the constellation Octans. It orbits the star LHS 475 and was the first exoplanet confirmed by the James Webb Space Telescope. The planet completes one orbit every two days and has a diameter 99% that of Earth, making it one of the closest matches to our planet in terms of size.
Its radius is 99% of Earth’s, and its mass is about 91.4% of Earth’s. The planet is likely tidally locked, meaning one side always faces its star. Whether it has an atmosphere remains unknown; it may have none, but a pure carbon dioxide atmosphere—hard to detect—has not been ruled out. With a high surface temperature, the presence of clouds could indicate a Venus-like world, where thick carbon dioxide clouds dominate.
The Transiting Exoplanet Survey Satellite (TESS) first detected signs of a planet around LHS 475 using the transit method. On August 31, 2022, the James Webb Space Telescope’s NIRSpec instrument observed the planet during two transits and recorded its transmission spectrum. The confirmation was announced on January 11, 2023.
Quick Facts
- Extrasolarplanet
- yes
- Apsis
- astron
- Discoverer
- James Webb Space Telescope
- Discovered
- 2023
- Discovery Method
- Transit
- Period
- 2.0291±0.0000 d
- Star
- LHS 475
Facts from the source article.
Lore & Background
LHS 475 b was first indicated by the Transiting Exoplanet Survey Satellite (TESS) through transit information. On August 31, 2022, the James Webb Space Telescope's NIRSpec instrument captured the exoplanet with just two transit observations and observed its transmission spectrum. Confirmation of the planet was published on January 11, 2023.
The planet is most likely tidally locked and completes an orbit every 2 days. It is very hot, though its exact temperature is not specified. It is not yet known whether LHS 475 b has an atmosphere; it is possible that it does not, but some atmospheric compositions have not been ruled out, such as an atmosphere made up of 100% carbon dioxide, which is difficult to detect. If clouds are detected on its surface, this could suggest that LHS 475 b is similar to Venus, which has an atmosphere made up of carbon dioxide surrounded by thick clouds.
Reader's Guide
LHS 475 b holds significance as the first extrasolar planet confirmed by the James Webb Space Telescope, demonstrating the telescope's capability to characterize small, rocky worlds. Its radius is 99% of Earth's, making it one of the most Earth-sized exoplanets known. The planet's mass, at 91.4% of Earth's, further reinforces its terrestrial nature. Its legacy lies in being a benchmark for atmospheric studies of Earth-like exoplanets; the uncertainty about its atmosphere—whether it is absent, or composed of pure carbon dioxide—highlights the challenges and potential of future observations. The possibility of a Venus-like scenario, with thick carbon dioxide clouds, adds to its comparative planetary science value. As a nearby target (40.7 light years away) in the constellation Octans, it remains a key object for understanding the diversity of terrestrial worlds beyond the Solar System.
Did You Know?
- LHS 475 b is 99% the diameter of Earth.
- It was confirmed by the James Webb Space Telescope on January 11, 2023.
- The planet orbits its star every 2 days and is likely tidally locked.
- Its atmosphere may be 100% carbon dioxide, or it may have no atmosphere at all.
More in Transiting Exoplanets, Part 4 1-24
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