News of exoplanet discoveries keeps rolling in. Astronomers from the University of Nevada, Las Vegas and NASA Ames Research Center in Moffatt Field, California, analyzing new exoplanet data collected through by NASA’s Kepler Space Telescope, have just identified a population of at least 24 new exoplanet star systems that could possess what are called “hot Earths.”
The new findings, reported in the journal Proceedings of the National Academy of Sciences, are illustrative of a star system formation that results in a very unique form of planetary architecture.
“A hot Earth, as defined by the researchers of this study, was a planet that was less than twice the radius of the Earth and had an orbital period less than two days,” UNLV astronomer Jason Steffen, the lead author of the study, tells Inverse. “Such planets would be orbiting at a distance that is only a few times the stellar radius.” Steffen and his co-author, Jeffrey Coughlin from NASA Ames, identified a unique planetary architecture in which a star has a single hot Earth in its orbit.
Steffen and Coughlin studied about 144 different star systems in a dataset compiled by Kepler. “What we found,” says Steffen, “is that at least one in six systems that have a hot Earth must be of this new type — where the hot Earth is far removed from its planetary siblings and perhaps as many as half of them are like this. Other hot Earths simply live in systems that are scaled down versions of the kind of planetary system that we’ve seen all along in the Kepler data.”
So, what’s so special about hot Earths? They seem to be Earth-like, but are they really like Earth — i.e. are they potentially habitable?
The answer is a resounding no: “The side of the planet facing the star would likely be molten and the back of the planet frigid,” says Steffen. “Like Mercury, only much more extreme.”
That’s a bummer. Still, there’s encouragement to be found in the new study, because they give us a bigger insight into the evolution of star systems and planets. “Producing a system with an isolated hot Earth is, apparently, one of the possible paths for planet formation to follow,” says Steffen. “By understanding these different outcomes and how likely they are to occur, we can get a better understanding of what processes are at play in the formation of planetary systems. It helps put the solar system into context.”
The pair didn’t find anything conclusive about the kinds of stars that produce hot Earths, though: “More data on these systems would be useful to better understand their origins,” Steffen says.
Nevertheless, Steffen and Coughlin are interested in learning how isolated hot Earths “became detached from their neighbors.” By virtue of being a rocky planet with a similar size to Earth, hot Earths are basically worlds that were one day on the path to becoming potentially habitable, but somehow ended up in an orbital period way too close to their host stars. Understanding how this divergence occurred could be key in allowing us to better identify potentially habitable planets and moons in other star systems.
Photos via NASA/JPL-Caltech