Space

Spitzer Detects Exoplanet Smaller than Earth: NASA

Brooke Miller
First Posted: Jul 19, 2012 09:10 AM EDT

A new discovery made by the astronomers using NASA's Spitzer Space Telescope claim that they have detected an exoplanet that is two thirds size of the planet Earth. The newly detected exoplanet known as UF-1.01, is located a mere 33 light years away making it much smaller than the nearest worlds to our solar system but much smaller than our planet.

Generally exoplanets are found circling the stars beyond our sun. Till date exoplanets discovered that are smaller than Earth are limited. Detailed studies were made on exoplanets with the aid of Spitzer, but UCF-1.01 is the first ever identified with the telescope, pointing to a possible role for Spitzer in helping discover potentially habitable, terrestrial-sized worlds.

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

Spitzer accidentally bumped into this hot new planet while Stevenson and his colleagues were studying the Neptune-sized exoplanet GJ 436b, which is already known to exist around the red-dwarf star GJ 436.

Based on the data collected from the observations made by spitzer 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.

Even NASA kepler space telescope uses this technique which relies on transits to detect exoplanets. The size and the distance of the exoplanet from the sun, is predicted based on the duration of a transit and the small decrease in the amount of light registered. It is observed that UCF-1.01's has a diameter of approximately 5,200 miles (8,400 kilometers), or two-thirds that of Earth. UCF-1.01 would revolve quite tightly around GJ 436, at about seven times the distance of Earth from the moon, with its "year" lasting only 1.4 Earth days. Given this proximity to its star, far closer than the planet Mercury is to our sun, the exoplanet's surface temperature would be more than 1,000 degrees Fahrenheit (almost 600 degrees Celsius). If this planet had any atmosphere, it would have surely evaporated. UCF-1.01 might therefore 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; that the extreme heat of orbiting so close to GJ 436 has melted the exoplanet's surface.

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

In addition to this a few more observation made by the researchers includes the existence of a third planet. Spitzer has observed evidence of the two new planets several times each. But even the most sensitive instruments were unable to measure exoplanet masses as small as UCF-1.01 and UCF-1.02, which are perhaps only one-third the mass of Earth. Because knowing the mass is required for confirming a discovery, the paper authors are now referring to both bodies' exoplanet candidates for now.

Till date approximately 1,800 stars were being identified by Kepler as candidates for having planetary systems, out of which three are verified to contain sub-Earth-sized exoplanets. Of these, only one exoplanet is thought to be smaller than the Spitzer candidates, with a radius similar to Mars, or 57 percent that of Earth.

"I hope future observations will confirm these exciting results, which show Spitzer may be able to discover exoplanets as small as Mars," said Michael Werner, Spitzer Project Scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "Even after almost nine years in space, Spitzer's observations continue to take us in new and important scientific directions."

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