A detection of the planet GJ 1132b atmosphere

Artistic concept of the exoplanet GJ 1132b and its star (Image courtesy MPIA)
Artistic concept of the exoplanet GJ 1132b and its star (Image courtesy MPIA)

An article published in “The Astronomical Journal” describes a research about the exoplanet GJ 1132b. A team led by Dr. John Southworth of Keele University and by Italian INAF associate Luigi Mancini used the 2.2-meter ESO/MPG telescope in Chile to directly study this super-Earth during its transit in front of its star and detect its atmosphere. This is the first direct evidence of the existence of an atmosphere for a planet similar in size to Earth, although it could look more like Venus.

The planet GJ 1132b, or Gliese 1132b, was discovered in 2015 and for its mass 1.6 times the Earth’s and its size about 1.4 times the Earth’s was immediately put at the center of research. Actually, they immediately saw that in many ways it’s unpromising because it’s so close to its star that its year lasts only 1.6 Earth days. The star is a really small red dwarf but the surface temperature is estimated to be around 230° Celsius (almost 450° Fahrenheit).

It could be a super-Venus rather than a super-Earth and in August 2016 in an article published in “The Astrophysical Journal” it was suggested that its atmosphere contained oxygen even when no life forms. In fact there was no certainty that there was an atmosphere of any kind but now this new research brought evidence that there is one, even if the information is still vague.

The fact that the planet GJ 1132b has such a short year was an advantage because it passes in front of its star all the time, making it possible to analyze many of its observations at various bands of wavelengths using the GROND (Gamma-Ray Burst Optical/Near-Infrared Detector) instrument mounted on the ESO/MPG telescope. The result is that the planet appears larger in the infrared band, suggesting that it has an atmosphere that makes it opaque to these wavelengths and transparent to others.

This technique doesn’t allow to understand with certainty the composition an exoplanet’s atmosphere so at the moment they can only make guesses based on the compounds opaque to infrareds. The importance of this discovery is that it’s the first direct evidence of the presence of an atmosphere for a planet like Earth or Venus, the more so because red dwarfs such as GJ 1132 are extremely common and research are focusing more and more on them.

What researchers can say is that the atmosphere of GJ 1132b is not the same as Venus’ because the detections are not compatible with those of a dense atmosphere composed almost entirely of carbon dioxide. It may be composed mainly of water or methane or a mixture of these compounds, therefore quite different from that of the Earth or Venus.

For more precise information on the atmosphere of the planet GJ 1132b the researchers intend to use other instruments such as the Hubble Space Telescope and ESO’s VLT. As happens with many interesting exoplanets, the big step forward will be obtained in the next few years, when the James Webb Space Telescope gets launched.

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