February 6, 2023

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Planet the same size as Earth discovered

Planet the same size as Earth discovered

“The discovery is very beautiful, a great observation. The data from James Webb looks very good, because of the powerful telescope. This bodes well for the future,” says Professor Ignas Snellen of Leiden University. Snellen researches exoplanets and their atmospheres. Exoplanets are planets orbiting a star other than the Sun.


Researchers at Johns Hopkins University in Maryland, US, announced the discovery of LHS 475 b after analyzing data from the James Webb Telescope. The planet betrayed its existence by spinning in front of its sun. Because of this, Webb saw a decrease in the star’s light each time the planet passed by.

“We can observe space in a different way with James Webb,” Snellen explains. “This discovery was made through the transit measurement method, where the difference in starlight indicates something about a planet as it passes in front of its star.”

What makes the James Webb Telescope unique is that it can take measurements of a planet’s atmosphere. This indicates that LHS 475 b is not like Earth in every way.

It is several hundred degrees warmer, and although it is not yet 100 percent certain whether it has its own atmosphere, a number of scenarios can be ruled out. For example, a methane-like atmosphere has not been measured as on Titan, a moon of Saturn. The researchers also ruled out the existence of a hydrogen-only atmosphere.

hundreds of temperatures

LHS 475 b has been carefully compared to Venus, which has an atmosphere that’s more than 95 percent carbon dioxide. “NASA is exploring the carbon dioxide atmospheric option,” Snellen says.

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“The temperature on Venus and on the detected planet is several hundred degrees. But we will need to do more atmospheric measurements to determine if LHS 475 b is really like Venus.”

Snellen has high expectations from these studies. “The James Webb telescope can also measure the temperature of a planet. This is the next step,” says Snellen. “When the planet passes behind the star, it’s not visible and you don’t measure its temperature. That way you can finally determine what kind of gas the planet is made of.” Snellen does not rule out the presence of a carbon dioxide atmosphere.

“But an exoplanet can also be a bare rock. The star the planet orbits around is a so-called red dwarf. These stars are very energetic and emit radiation and charged particles. They can cause planetary atmospheres to disappear completely.”


The James Webb Telescope is the largest and most powerful space telescope ever built. It was launched at the end of last year from the European Space Agency’s base in French Guiana and is the successor to the Hubble Telescope.

“We can use James Webb to determine the composition of the atmosphere, and therefore determine whether a planet is similar to Venus, Mars or Earth, for example,” Snellen explains. “A next-generation telescope could look at the atmosphere and look for oxygen, for example. Then we can really say whether a planet is habitable.”