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06 April 2017

Discovery! Atmosphere Spotted on Nearly Earth-Size Exoplanet in First


For the first time, scientists have detected an atmosphere around a planet beyond our solar system that's just a little bit larger than Earth.

The exoplanet GJ 1132b, which orbits the dwarf star GJ 1132, is located about 39 light-years away from Earth. It has a radius about 1.4 times that of Earth and is 1.6 times Earth's mass, according to the new study. When the planet was first discovered, researchers called it a potential Venus twin because it's a rocky world with a very high surface temperature — and now, they've found that the planet and Venus might have a thick atmosphere in common, too (although it would have a different composition).


While observers have pinpointed atmospheres around much larger, Jupiter-like gas giants orbiting other stars — and a larger super-Earth, about eight times Earth's mass — this is the first evidence of an atmosphere around an exoplanet that's near Earth's size, the study's researchers said. Researchers can use planets' atmospheres to try and determine if these worlds are suitable for life as we know it on Earth, or even to identify potential traces of life recorded there.

"While this is not the detection of life on another planet, it's an important step in the right direction: The detection of an atmosphere around the super-Earth GJ 1132b marks the first time that an atmosphere has been detected around an Earth-like planet other than Earth itself," John Southworth, a researcher at Keele University in the United Kingdom and first author on the new work, said in a statement from the university.

The astronomers captured images of the planet's star using a telescope at the European Southern Observatory (ESO) in Chile. The researchers measured the star system with seven different wavelengths and used small dips in the star's brightness to determine the radius of the planet passing by during its 1.6-day orbits, according to a statement from the Max Planck Institute for Astronomy, which collaborated on the research. They were able to further clarify the planet's radius.


But the researchers also found something strange, they said: One of the wavelengths showed a larger dip in brightness than the others each time the planet passed by. This world, for some reason, appeared larger at that wavelength than at others, suggesting that the planet had a surrounding atmosphere that this wavelength couldn't penetrate, the researchers said.

While Earth's atmosphere is mostly nitrogen with a large oxygen component, and Venus' is a thick shroud of carbon dioxide, the researchers said that GJ 1132b's atmosphere is likely rich in water vapor or methane, based on their measurements. (It could be "a 'water world' with an atmosphere of hot steam," Southworth said.)

The discovery is particularly exciting because M-dwarf stars like GJ 1132 are the most common star type in the galaxy — and make up 20 of the 30 nearest stars to Earth — but their high levels of activity, like flares and streams of particles, could potentially blow away any forming atmosphere on nearby planets. If planets like GJ 1132b can maintain atmospheres, it opens up the possibility that many more potentially habitable worlds exist in the universe, the researchers said.

Going forward, GJ 1132b's atmosphere will be a high-priority target for study with the Hubble Space Telescope, ESO's Very Large Telescope and the future James Webb Space Telescope, launching in 2018, the researchers added.

The new work was detailed March 31 in The Astrophysical Journal.