Illustration by D. Ducros/CNES 2006; (inset)LESIA/OBSPM

Planet hunter. The Earth-orbiting, French-built COROT space telescope has been looking for the transits of certain Earth-like planets since 2006.

Hellish 'Super-Earths' Likely Prevalent Throughout Our Galaxy

Although it's only a little bigger than Earth and is made of the same ingredients, this planet is no paradise. It orbits so close to its parent star that its surface is a sea of molten lava, its atmosphere swirling with silicate vapor.

The galaxy is rife with hellish worlds like this one, astronomers now predict based on theoretical studies.

New findings suggest that Earth-like planets are common throughout the galaxy. However, when Kevin Schlaufman, a graduate student at the University of California, Santa Cruz, and colleagues used computer models to simulate a theoretical extrasolar planet population, they found that a new breed of super-Earths was also surprisingly prevalent. The team's results, to be published in The Astrophysical Journal Letters, indicate that these rocky planets would range up to 10 times the mass of Earth and would orbit their host stars in 24 hours or less, as does the planet described here.

"If our model and analysis are correct, these very hot super-Earths would be the hottest planets in the galaxy," says Schlaufman. "Their surfaces would likely be oceans of lava, possibly in the process of being vaporized by their own stars."

Such planets typically form early in the history of a solar system and are farther away from their stars than Earth is from the sun. So how does an Earth-mass planet end up so close to its parent star? The short answer is via inward migration. Over about 100,000 years, the planets interact with their surrounding, gas-rich planetary disks, causing their orbits to swiftly move inward toward their parent stars. Schlaufman notes that life on these scorching planets is totally out of the question.

Natalie Batalha, the deputy science team lead for NASA's Kepler mission to find Earth-like worlds, says that Kepler's detection of many planetary candidates smaller than Neptune in close orbits around their stars suggests that Schlaufman and colleagues' models "might be right on target." And the project is expected to announce the discovery of a slew of such hot super-Earths by early next year.

"Such super-Earths would be different from anything in our solar system," said Eric Ford, an astronomer at the University of Florida, Gainesville, who was not involved in the study. "One side is continuously illuminated and scorching hot, while the other side remains in perpetual night."

And conditions will only get worse. Schlaufman says that the same effects that cause tides on Earth also force very hot super-Earths to begin death spirals into their parent stars.

The side of the planet not facing the star will be pulled in one direction, and the side of the planet facing the star will be pulled in another, says Schlaufman. Eventually, before being incinerated, the super-Earth will be ripped apart.

Posted in Space