Hydrogen and Helium Atmosphere Observed on Super Earth 55 Cancri e

Published on February 22, 2016 at 10 a.m. by Jacqueline Taylor  
Using the ever helpful Hubble Space Telescope and newly-developed analysis techniques, UK scientists have observed that a super-Earth has a helium and hydrogen atmosphere. This is the first time atmospheric gases have been detected in this class of exoplanets, giving scientists their first clues into how super-Earths like 55 Cancri e formed and evolved over time. Super-Earths are the most common planet type in our galaxy, named for being smaller than gas giants but larger than the Earth. Located 40 light years away in planetary system 55 Cancri, the exoplanet has a mass eight times that of Earth, and is inferred to have a carbon-rich interior. Additionally, the presence of the highly poisonous prussic acid, hydrogen cyanide, was detected, meaning that the atmosphere could also be rich in carbon. Unusual for super-Earths, 55 Cancri e orbits very close to its host star, giving it a short 18-hour year, and surface temperatures of over 2000 degrees Celsius. It is actually this unusual behavior that allows the analysis observing its dry atmosphere to be conducted. Hubble is equipped with a camera, called Wide Field Camera 3, which scanned the planet during its transits in front of the star, allowing for software to reveal the spectrum of light surrounding the planet. The observations suggest that the super-Earth miraculously managed to retain much of the hydrogen and helium from the nebula from which it was created. Super-Earths GJ1214b and HD97658b were also observed by Hubble, but due to the thick clouds covering their surfaces, were deemed to have atmospheres composed of molecules much heavier than hydrogen. More analyses will be performed on 55 Cancri e in the coming years as new generations of infrared telescopes are invented and deployed, such as WFIRST.