Using a ground-based telescope, researchers have found an Earth-like planet which hosts an atmosphere, but don't get excited just yet.
Located 39 light-years away in the Vela constellation in the southern hemisphere, the planet called GJ 1132b (or Gliese 1132b) orbits a red dwarf star and is considered uninhabitable as it has an estimated surface temperature of 370 °C. Dr John Southworth, the lead researcher from Keele University, expressed his extreme skepticism about the possibility of life on Gliese 1132b:
"To my knowledge the hottest temperature that life has been able to survive on Earth is 120C and that's far cooler than this planet."
Still, it's cool enough to support an atmosphere, and Southworth and the rest of the team were thrilled to discover it. Using the 2.2-meter ESO/MPG telescope in Chile, they were able to identify a very slight decrease in brightness as the planet passed in front of its star. This is actually a method to discover new planets, and it's how Gliese 1132b itself was discovered. They calculated that the dip in brightness indicates the existence of an atmosphere around the planet.
While previous efforts have identified atmospheres around other planets, it's the first time an atmosphere was reported around a rocky, small, Earth-like planet. Southworth explains:
“With this research, we have taken the first tentative step into studying the atmospheres of smaller, Earth-like, planets. We simulated a range of possible atmospheres for this planet, finding that those rich in water and/or methane would explain the observations of GJ 1132b. The planet is significantly hotter and a bit larger than Earth, so one possibility is that it is a "water world" with an atmosphere of hot steam.”
We don't know much about the structure and composition of this atmosphere. The one thing we do know is that it's likely nothing like Earth's, says Tom Louden, a physicist at the University of Warwick who wasn’t involved in the study.
“This detection implies it has a massive and extended atmosphere, composed largely of hydrogen and helium, probably more similar to Uranus or Neptune than to Earth,” said Louden. “To be clear, an atmosphere that we would think of as Earth-like would be completely invisible to these observations, and to all other currently existing telescopes.”
Atmospheres are most easily discovered around Jupiter-like planets -- especially 'hot Jupiters,' gas giants like Jupiter, but which are located much closer to their star. Prior to this discovery, two other super-Earths were known to have atmospheres, but this one is the smallest -- weighing just 1.6 Earth masses, with a radius just 1.4 times larger than Earth’s, it's officially the smallest exoplanet we know of with an atmosphere.
The discovery is extremely encouraging because, for one, it shows that the method has improved dramatically, and will likely result in the discovery of more Earth-like planets. If with today's technology we can discover an atmosphere, then discovering planets should be much more accessible. Secondly, low-mass stars like the one around which Gliese 1132b orbits are very abundant in our galaxy, and are known to host numerous rocky planets -- potentially, lots of Earth-like planets. However, these planets are exposed to high levels of X-rays and ultraviolet light which can vaporize an atmosphere. If this one has survived for billions of years, there's no reason to believe others haven't also survived.
However, it's not completely impossible for Gliese 1132b to host life. The planet receives 19 times more stellar radiation than Earth, but it might be tidally locked -- meaning that one part of the planet is much hotter than the other. If this is the case, there might be a sweet spot with low enough temperatures for life to survive... but I wouldn't get my hopes up.
Journal Reference: John Southworth, Luigi Mancini, Nikku Madhusudhan, Paul Mollière, Simona Ciceri, and Thomas Henning -- Detection of the Atmosphere of the 1.6 M ⊕ Exoplanet GJ 1132 b.