Smells like teen spirit, er, I mean like hydrogen and helium laced with bitter almonds. Using data gathered with the Hubble Space Telescope and new analysis techniques, the exoplanet 55 Cancri e was found to have a dry atmosphere bereft of water vapor but rich in the simplest elements that are also the most common in the universe. It orbits its host star 55 Cancri so closely that a year there lasts 18 hours, and the temperature cooks at around 3,600° F (2,000° C). Hot! No, the livin’ ain’t easy on this extrasolar planet, but it’s the first super-Earth to have its atmosphere analyzed.
A super-Earth is a planet more massive than our own but considerably less than the ice-giants Uranus and Neptune. As instrumentation and measurement have become ever more precise since the first extrasolar planet discovery in 1995, we’ve gone from detecting only the most massive, Jupiter-like worlds down to super-Earths and even a few Earth-mass planets. Astronomers find planets beyond our solar system primarily by measuring the drop in light as they transit their host suns or by the gravitational wobble they induce in those same stars.
The next step after nailing down size and orbit is to determine atmospheric and surface conditions with the goal of finding planets that might be habitable. 55 Cancri b is one of five planets orbiting its parent sun, all of which formed from a cloud of gas and dust similar to the one that birthed our own solar system and sun. Eight times more massive than Earth, it held onto the nebula’s lighter gases hydrogen and helium much like Jupiter and Saturn did.
Super-Earths like 55 Cancri e are thought to be the most common type of planet in our galaxy, though this one’s unusual in orbiting its sun-like star so closely. Traces of the bitter almond-smelling gas hydrogen cyanide found in its air is a marker for carbon-rich atmospheres.
“If the presence of hydrogen cyanide and other molecules is confirmed in a few years time by the next generation of infrared telescopes, it would support the theory that this planet is indeed carbon rich and a very exotic place,” concludes Jonathan Tennyson of University College London, who was part of the team making the discovery. “Although hydrogen cyanide, or prussic acid, is highly poisonous, so it is perhaps not a planet I would like to live on!”
