Researchers say they have confirmed an exoplanet—a planet orbiting another star—using NASA’s new James Webb Space Telescope (JWST) for the very first time.
The planet, known as “LHS 475 b”, is almost exactly the same size as Earth. Researchers say the planet is a few hundred degrees warmer than Earth.
Presenting their findings at an American Astronomical Society (AAS) event in Seattle on Jan. 11, researchers from Johns Hopkins University Applied Physics Laboratory (JHUAPL) described how they used the next-generation Webb telescope to confirm an exoplanet.
LHS 475 b is relatively close, only about 41 light-years away, in the Octans constellation.
Webb’s Near-Infrared Spectrograph instrument captured two transit observations—as the planet passed in front of its star, slightly dimming its light—in August and September last year.
What was revealed is a rocky Earth-sized planet that completes an orbit of its sun in just two days.
It’s also warm—a few hundred degrees warmer than Earth.
“By fitting our transit model to these observations and ruling out various false positive scenarios that could lead to a planet, these pristine data helped to validate and confirm the discovery of this Earth-size exoplanet. And moreover, the depth of the transit, the amount of light blocked gives us a measure of the planet’s radius, which turns out to be almost exactly the same as that of the earth. It’s 99 percent earth’s diameter plus or minus, about half a percent,” explains researcher Jacob Lustig-Yaeger from JHUAPL.
“It’s really exciting to get this glean of data on earth-sized planets. And though this planet shares the same radius as Earth, that’s likely the only similarity it has with Earth, because it is about a couple hundred degrees warmer than the Earth.”
Although data shows this is an Earth-sized planet, researchers don’t yet know if it has an atmosphere.
While it’s possible the planet has no atmosphere, researchers say there are some atmospheric compositions they are yet to rule out, such as a purely carbon dioxide atmosphere.
“This planet very well could be an airless body that has lost any atmosphere that it once had,” explains Lustig-Yaeger.
“But it also might possess a compact atmosphere that we are not sensitive to that could be composed of carbon dioxide, could be a thin atmosphere that would produce very small spectroscopic features, or it could be a thick atmosphere composed of carbon dioxide like Venus, that has a high-altitude cloud that would also produce a very flat transmission spectrum.”
NASA and the European Space Agency’s $10 billion successor to the Hubble Space Telescope rocketed away at the end of 2021 and has been observing the cosmos in the infrared since summer 2022.
Scientists hope to behold the dawn of the universe with Webb, peering all the way back to when the first stars and galaxies were forming 13.7 billion years ago.
The observatory is positioned 1 million miles (1.6 million kilometers) from Earth.
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