Most worlds orbiting distant suns are larger than Earth. It makes sense we’d see the biggest ones first. But today (July 18, 2012), astronomers using NASA’s Spitzer Space Telescope and at the University of Central Florida announced the possible detection of an exoplanet only two-thirds the size of Earth, orbiting the red-dwarf star GJ 436, just 33 light-years away. If they’re right, this might be the nearest world to our solar system that is smaller than our home planet.
They’re calling the new, diminutive exoplanet UCF-1.01. Kevin Stevenson from the University of Central Florida in Orlando is lead author of a paper about this new world, which has been accepted for publication in The Astrophysical Journal. He said:
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 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.