GJ 1214 b is an extrasolar planet orbiting the star GJ 1214. It is approximately 40 light years from the Sun in the Ophiuchus constellation, which is located around the celestial equator.
Mass: 3.91 x 1025 kg
Composition: Dense water vapour atmosphere, possibly has a water-based core
Orbit: 1.58 Earth days
GJ 1214 b, also called Gliese Jahreiss 1214 b, was discovered in 2009 by astronomers working on the MEarth Project, a search for extrasolar planets orbiting red dwarf stars. The project is based at the Harvard-Smithsonian Center for Astrophysics. This was the first time that ground-based telescopes had identified a distant planet. Amateur astronomers using similar telescopes with a good camera are able to observe it. The star GJ 1214 is named after German astronomers Wilhelm Gliese and Hartmut Jahreiss who observed and produced a catalogue of nearby stars.
The planet is known as a super-Earth, also called a gas dwarf, meaning it has a mass greater than that of the Earth, but less than the gas giants Neptune and Uranus. The term does not imply that the planet is habitable. It orbits its star every 38 hours at a distance of two million kilometres. This is 70 times closer to its star than Earth is to the Sun.
In December 2010, astronomers published the results of a spectral analysis of the GJ 1214 b atmosphere that was conducted using the European Southern Observatory Very Large Telescope at Cerro Paranal in the Atacama Desert, northern Chile.
According to a spectral analysis of both the planet’s atmosphere as it moved in front of its star and infra-red light from the star that passed through the planet’s atmosphere, GJ 1214 b’s atmosphere is thin. It may consist of water vapour or steam, or consist of hazes or high clouds similar to those observed on Venus and Titan, one of Saturn’s moons. A hydrogen and helium atmosphere similar to those on Neptune and Uranus has been ruled out. However, the presence of steam could obscure any detection of hydrogen in the planet’s atmosphere.
The structure of GJ 1214 b is a matter of speculation. It may have a rocky core or a water core and surface ice similar to the Galilean moons of Jupiter. In March 2011, NASA astronomers announced that an analysis of older data from the Spitzer space telescope, together with newer observational data of the planet, led them to conclude that the water vapour concentration in its atmosphere could range between 10 and 50%.