Super-Earths are planets larger than our own (in this case, twice as big and eight times as massive) but not as large as the towering gas giants.
While these planets may be more Earth-like than others, most of them are totally uninhabitable. Janssen is no exception: Because of its close proximity to its host star, Janssen boasts a surface temperature of over 3,600 degrees Fahrenheit.
Now, thanks to data from the Hubble, scientists have confirmed that this rocky hell-scape lacks water. They detected signs of hydrogen and helium in the atmosphere but no water vapor to speak of. Hints of hydrogen cyanide could indicate a carbon-rich atmosphere, according to the scientists. That would make sense, since Janssen's mass and radius led scientists to believe it might be carbon-rich — earning it the nickname of "diamond planet."
This is the first time scientists have successfully detected an atmosphere in a super-Earth, though they've tried to use the same method a couple of times before. Janssen was more forthcoming because of its super-close proximity to its host star. I mean, super close. A year on Janssen lasts only 18 hours.
Scientists can determine the makeup of a planet's atmosphere by watching as it transits in front of its host star. The way the passing planet changes the light of the star behind it — light that's passing through the planetary atmosphere on its way to our line of sight — can reveal what molecules are clinging to it. Because Janssen is still tied to those stellar apron strings and passes in front of the alien sun so frequently, researchers were able to collect lots of data in a short amount of time.
With its burning-hot surface and its toxic hydrogen cyanide, Janssen definitely isn't an exoplanet worth visiting. But as researchers improve techniques for puzzling out planetary characteristics, we up our odds of stumbling upon a super-Earth that's actually super Earth-like.