Spitzer Telescope Finds Evidence for an Exoplanet Smaller than Earth, 33 Light-Years Away

Posted on July 18, 2012

Astronomers using NASA's Spitzer Space Telescope have detected what they believe is a planet two-thirds the size of Earth. The diameter of the planet is about 5,200 miles. The exoplanet candidate, called UCF-1.01, is located 33 light-years away, making it possibly the nearest world to our solar system that is smaller than our home planet. Only a handful of exoplants smaller than Earth have been found so far. An Artist's impression of UCF-1.01 is pictured above.

Kevin Stevenson from the University of Central Florida in Orlando and lead author of the the paper accepted for publication in The Astrophysical Journal, says, "We have found strong evidence for a very small, very hot and very near planet with the help of the Spitzer Space Telescope. Identifying nearby small planets such as UCF-1.01 may one day lead to their characterization using future instruments."

The hot new planet candidate was found unexpectedly in Spitzer observations. Stevenson and his colleagues were studying the Neptune-sized exoplanet GJ 436b, already known to exist around the red-dwarf star GJ 436. In the Spitzer data, the astronomers noticed slight dips in the amount of infrared light streaming from the star, separate from the dips caused by GJ 436b. A review of Spitzer archival data showed the dips were periodic, suggesting a second planet might be blocking out a small fraction of the star's light.

Stevenson led a team that analyzed data from the Canada-France-Hawaii Telescope in Hawaii and the Very Large Telescope in Chile to verify that the signals he was seeing were not caused by other astrophysical sources. The team also analyzed a large number of high-precision measurements of the star's wobble. As expected for planets this small, no signal was present.

The planet is likely to be extremely hot. The exoplanet's surface temperature would be more than 1,000 degrees Fahrenheit (almost 600 degrees Celsius). The surface of the planet might resemble a cratered, mostly geologically dead world like Mercury. Paper co-author Joseph Harrington, also of the University of Central Florida and principal investigator of the research, suggested another possibility. He says the extreme heat of orbiting so close to GJ 436 may have melted the exoplanet's surface.

Harrington says, "The planet could even be covered in magma."

In addition to UCF-1.01, Stevenson and his colleagues noticed hints of a third planet, dubbed UCF-1.02, orbiting GJ 436. You can read more about the discovery here.

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