For the first time, astronomers have discovered a class of exoplanets whose atmospheres have been seared away by heat, removing any doubts about what happens when a rocky object wanders too close to a star. Theorists have long speculated that exoplanets snuggled right up next to their host stars would be subject to "stripping", or erosion of the atmosphere by high-energy radiation. Now, using data collected by NASA's Kepler Space Telescope, a team of astrophysicists at the University of Birmingham is reporting the very first observational evidence of these shriveled raisins. The findings are published today in Nature Communications.
"Our results show that planets of a certain size that lie close to their stars are likely to have been much larger at the beginning of their lives," study co-author Guy Davies said in a statement. "For these planets it is like standing next to a hairdryer turned up to its hottest setting."
The planets Davies and his co-authors studied are "super Earths", rocky worlds larger than Earth but smaller than Neptune that are abundant in the cosmos but curiously absent from our own solar system (although that might change if and when astronomers discover Planet nine).
Despite how exotic these blistering hellscapes sound, they may foreshadow what's to come in our own distant future. After all, as the Sun grows hotter and brighter over the next billion years, the extra radiation will start to cook our fragile biosphere, eventually boiling away the oceans and rendering the entire surface of the Earth uninhabitable. Whether our planet will eventually be stripped of its atmosphere too isn't certain -- but given the mounting evidence we're beginning to see all over the galaxy, I don't think we want to be around to find out.
Top: A planet having its atmosphere stripped by a star's heat. Image: Peter Devine