Atmosphere detected around an Earth-like planet

An atmosphere has been detected for the first time around a planet with a mass and radius similar to Earth.

The atmosphere of planet GJ 1132b is opaque to infrared wavelengths, suggesting it is rich in water or methane both potential precursors for life.
Credit: MPIA

An atmosphere has been detected around an exoplanet with a mass and radius close to that of Earth for the first time, and appears to be rich in water. It's thought that an atmosphere is necessary to create the conditions needed for life to evolve and so finding one around a planet so like our own brings researchers one step closer to finding a second Earth.

Astronomers have begun attempting to observe exoplanet atmospheres, as their compositions can be used to search for signs of life. But such observations have currently only been done around gas giants and super Earths more than eight times Earth's mass.

Read more about the search for Earth 2.0 from BBC Sky at Night Magazine

This planet, GJ 1132b, however, is 1.6 Earth masses and 1.4 Earth radii in size and orbits a red dwarf star 39 lightyears away. Such stars have been targeted by recent hunts for exoplanet atmospheres as they lend themselves well to studying atmospheres. Not only are they dimmer, making the brightness fluctuations of passing planets clearer, but researchers have already created very precise stellar models of red dwarfs. This means that astronomers can calculate the star’s size to a great degree of accuracy, allowing them to deduce the planet’s size equally well. They are also among one of the most common stars in the Galaxy, meaning that planets with atmospheres similar to GJ 1132b could be relatively common.

When astronomers imaged GJ 1132b with the European Southern Observatory’s 2.2m ESO/MPG telescope, they discovered that at some infrared wavelengths the planet appeared much larger than at other wavelengths, suggesting the planet is surrounded by an atmosphere that is opaque at these wavelengths.

There are several possible explanations of what this atmosphere could be like. The best fit to the observations currently is an atmosphere rich in water and methane, however more study is needed to truly understand the climate. The planet has already been marked up as a high priority target for the Hubble Space Telescope, ESO’s Very Large Telescope and the James Webb Space Telescope, due for launch in 2018.


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