Astronomers have detected and analyzed the atmosphere of a “super-Earth” exoplanet for the first time. And as it turns out, this “super-Earth” isn’t so super when it comes to being habitable.
Using data gathered by the Hubble Space Telescope and new analysis techniques, the scientists found that exoplanet 55 Cancri e has a dry atmosphere without any indications of the presence of water vapor. Indeed, they found that it’s mostly hydrogen and helium in composition.
But that’s not all that makes it hostile to life as we know it. 55 Cancri e also has a mass of eight Earths.
The results of their study will be published in the Astrophysical Journal and is also present in an open-source format on arXiv.
“This is a very exciting result because it’s the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth,” explains Angelos Tsiaras, a PhD student who developed the analysis technique along with his colleagues Ingo Waldmann and Marco Rocchetto. “The observations of 55 Cancri e’s atmosphere suggest that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it originally formed.”
As an aside, super-Earths like 55 Cancri e are believed to be the most common type of planet in our galaxy. They are named ‘super-Earth’ because they have a mass far greater than that of the Earth but are still much smaller than the gas giants in the Solar System.
55 Cancri e is unusual in the fact that it orbits very close to its parent star. A year on the exoplanet lasts for only 18 hours and temperatures on the surface are estimated to reach around 2000 degrees Celsius (3632ºF). Due to the exoplanet orbiting its bright parent star at such a small distance, the team was able to use new analysis techniques to extract information about the planet during its transits in front of the host star.
“This result gives a first insight into the atmosphere of a super-Earth. We now have clues as to what the planet is currently like and how it might have formed and evolved, and this has important implications for 55 Cancri e and other super-Earths,” said Giovanna Tinetti who is also part of the team.
Interestingly, the data also seems to indicate the presence of hydrogen cyanide, an indicator for carbon-rich atmospheres. “Such an amount of hydrogen cyanide would indicate an atmosphere with a very high ratio of carbon to oxygen,” notes Olivia Venot who developed an atmospheric chemical model of 55 Cancri e.