For the first time, astronomers have detected an atmosphere surrounding a "super-Earth" exoplanet which is close in size to Earth, another key step towards finding a world similar in size to ours that is also habitable. It's not Earth 2.0 just yet, but it's another indication that we are getting closer to finding a world that reminds us of home.
The planet, GJ 1132b, orbits the red dwarf star GJ 1132 (also known as Gliese 1132) in the constellation Vela, at a distance of only 39 light-years, very close by in cosmic terms. It is only 1.6 Earth masses and 1.4 Earth radii, making it a "super-Earth," a type of exoplanet which is larger than Earth but smaller than Uranus or Neptune.
Previously, an atmosphere had also been detected round the super-Earth 55 Cancri e, but that planet is 8 times the mass of Earth. GJ 1132b is much closer in size to our planet. Other atmospheres detected so far have been on larger gas-giant type worlds.
The observations were made using the GROND imager at the 2.2 m ESO/MPG telescope of the European Southern Observatory in Chile, which studied the planet simultaneously in seven different wavelength bands. The project was conceived, and the observations coordinated, by Luigi Mancini, formerly of the Max Planck Institute for Astronomy (MPIA), who now works at the University of Rome Tor Vergata. Other MPIA team members were Paul Mollière and Thomas Henning. The planet's atmosphere was studied as the planet transited in front of its star.
"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.
"If the technology can detect an atmosphere today, then it bodes well for being able to detect and study the atmospheres of even more Earth-like planets in the not-too-distant future," said Marek Kukula, an astronomer at the Royal Observatory Greenwich.
GJ 1132b and Earth
Observing the atmospheres of planets in other solar systems is difficult, and so not a lot is known yet about the composition of that atmosphere, but the new observations suggest it is opaque to one of the infrared wavelengths seen. Simulations of different atmospheric models indicate that an atmosphere rich in water and methane could explain the observations very nicely. GJ 1132b could be a water world with a hot, steamy atmosphere. It is also thought that the atmosphere is probably quite clear, with few if any thick cloud formations. On rocky planets like Earth, methane could be a possible sign of biology, although it can form from geological processes as well, and on larger gas giants, it is simply a primordial gas left over from a planet's formation.
The composition of the planet itself could range from nearly a Earth-like rocky interior, with ~70% silicate and ~30% iron, to a substantially water-rich world.
Previous studies of this planet suggested it is very hot, perhaps even Venus-like. But if the atmosphere contains a lot of water vapor and/or methane, that would make it quite different from Venus. Perhaps somewhere in between Venus and Earth? Early on, astronomers had thought that Venus might be wet and steamy, until spacecraft showed the atmosphere to be made of carbon dioxide, with surface temperatures hot enough to melt lead.
M-dwarf stars like GJ 1132 are the most common type in the galaxy. They are known however, to be very active, with flares that could strip away atmospheres from some unlucky planets. The discovery of a substantial atmosphere on GJ 1132b, however, shows that such planets can indeed keep their atmosphere in some cases.
GJ 1132b will likely be a high-priority target for other telescopes such as the Hubble Space Telescope, ESO’s Very Large Telescope, and the upcoming James Webb Space Telescope in 2018. In the near future, telescopes will also be able to study the atmospheres of smaller, rocky exoplanets for signs of possible biomarkers - gases such as oxygen, nitrogen or methane.