Washington, Jul 19 (IANS): US astrophysicists have detected what could be the first exoplanet, only two-thirds the size of Earth but without an atmosphere, located right around the corner, cosmically speaking, at a mere 33 light-years away.

Called UCF 1.01, the exoplanet is close to its star, so close that it goes around the star in 1.4 days. The planet's surface likely reaches temperatures of more than 538 degrees Celsius.

Researchers from The University of Central Florida (UCF) believe that it has no atmosphere, is only two-thirds the gravity of Earth and that its surface may be volcanic or molten, the Astrophysical Journal reports.

"We have found strong evidence for a very small, very hot and very close-by planet with the help of the Spitzer Space Telescope. This discovery is a significant accomplishment for UCF," said Kevin Stevenson, a recent doctoral graduate from the UCF, who led the study, according to a UCF statement.

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 yielded 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 post-doctoral scholar at the University of Chicago.

So he, UCF planetary sciences professor Joseph Harrington and UCF graduate student Nate Lust began looking at the data. They sifted through hundreds of hours of observations collected from Spitzer, the Deep Impact spacecraft, the ground-based Very Large Telescope in Chile and the Canada-France-Hawaii Telescope near the summit of Mauna Kea in Hawaii.

This transit technique, used by a number of telescopes, including NASA's Kepler space telescope, relies on these tiny, partial eclipses to find exoplanet candidates.

Spitzer has performed science work on known exoplanets before, but UCF-1.01 represents the first time Spitzer has made a transit discovery.