[LINK] "Scientists Discover Exoplanet Neighbor Smaller Than Earth"

[rfmcdonald]

Science Daily reports that a team of astronomers may have found one of the smallest exoplanets yet discovered, a molten rocky world orbiting Gliese 436, a red dwarf star also known as Ross 905 33.1 light years away in the constellation Leo. Already, it has been known since 2007 that the star supports a "hot Neptune" planet. This rocky world orbits its dim star still closer.

The exoplanet candidate called UCF 1.01, is close to its star, so close it goes around the star in 1.4 days. The planet's surface likely reaches temperatures of more than 1,000 degrees Fahrenheit. The discoverers believe that it has no atmosphere, is only two-thirds the gravity of Earth and that its surface may be volcanic or molten.

"We have found strong evidence for a very small, very hot and very close-by planet with the help of the Spitzer Space Telescope," said Kevin Stevenson, a recent Ph.D graduate from UCF and lead author of the paper, which appears online tomorrow in The Astrophysical Journal. "This discovery is a significant accomplishment for UCF."

Stevenson and his colleagues were studying a hot-Neptune exoplanet, designated GJ 436b, already known to exist around the red-dwarf star GJ 436, when data revealed clues that led them to suspect there could be at least one new planet in that system, perhaps two.

The team noticed slight dips in the amount of infrared light streaming from the star. A review of Spitzer archival data showed that the dips were periodic, suggesting that a planet might be blocking out a small fraction of light as it passed in front of GJ 436, as seen from Earth.

"I could see these faint dips in the starlight and I wanted to determine their source. I knew that if these signals were periodic, they could be from an unknown planet," said Stevenson, who is now a postdoctoral scholar at the University of Chicago.

[. . .]

With the finding of UCF-1.01, GJ 436 is likely now home to the first multi-transiting-planet system described by a mission other than Kepler. Of the 1,800 stars identified by Kepler as candidates for having planetary systems, only three are verified to contain sub-Earth size exoplanets.

The depth and duration of a transit reveals basic properties of an exoplanet, such as its size and distance from a host star. In UCF-1.01′s case, its diameter is estimated at 5,200 miles, or two-thirds that of Earth, placing the world among the smallest on record. The team also noticed hints of yet another potential planet dubbed UCF-1.02, but its period was impossible to estimate.