Blue light observations of a super-Earth 40 light years from our planet suggest that it is a world with a thick, steamy water-rich atmosphere.
Japanese astronomers used the Subaru telescope to observe planetary transits of the super-Earth, which is located at the centre of the Milky Way.
Astronomers had previously confirmed that this alien world has a thick atmosphere, but were unable to determine whether the atmosphere was primarily hydrogen or a steamy soup of water vapour.
Their findings confirm that the super-Earth has an atmosphere rich in water rather than hydrogen. Super-Earths are exoplanets orbiting a star outside of the solar system that are larger than Earth’s but smaller than those of ice giants such as Uranus or Neptune. Their planetary transits enable scientists to find changes in the wavelength in the brightness of the star, which indicate the planet’s atmospheric composition.
If scientists can determine the major atmospheric component of a super-Earth, they can then find out the planet’s birthplace and formation history.
The water world, named GJ 1214b is one of the more well-known super-Earths and was discovered by the ground-based MEarth Project in 2009.
This super-Earth is about 2.6 times Earth’s diameter and weighs almost seven times as much. It orbits a red-dwarf star every 38 hours at a distance of 2 million kilometres, giving it an estimated temperature of 230 degrees Celsius. Last year, the Hubble space telescope examined GJ 1214b when it crossed in front of its host star.
During such a transit, the star’s light is filtered through the planet’s atmosphere, giving clues to the mix of gases.
They found the spectrum of GJ 1214b to be featureless over a wide range of wavelengths, or colours, also suggesting the planet had a dense atmosphere of water vapour.
