article image

Spitzer discovers exoplanet candidate

Dr Amanda Doyle, Feature writer
Jul 19, 2012, 7:00 UTC

Sen—- NASA’s Spitzer Space Telescope may have accidentally discovered its first exoplanet, which is estimated to be only two thirds the size of the Earth.

Spitzer is often used to perform follow up observations of exoplanets in the infrared region of the spectrum, which can be useful for studying the atmospheres of exoplanets. Transiting exoplanets are discovered as they periodically block light from their host star. Astronomers using Spitzer to observe the already known Neptune-sized planet GJ 436b noticed that there were regular dips in the star’s infrared light, which suggests that another planet may be present.

The planet candidate, dubbed UCF-1.01, is estimated to have a size only two thirds that of the Earth. While NASA’s Kepler mission is now finding planets much smaller than the typical hot Jupiter gas giants, very few Earth-size planets have been discovered so far. Unfortunately, the small size of UCF-1.01 makes it difficult to confirm as an actual planet.

While transits can reveal information such as the radius and orbital period, the data contains no estimate of the mass of the transiting object. As such, it cannot be conclusively stated if the object is a planet or something else. The mass of UCF-1.01 can only be measured via the gravitational influence that it has on the host star, but this is very hard to detect for low mass objects. However, astronomers are confident that this particular candidate will be confirmed as a planet.

"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. "Identifying nearby small planets such as UCF-1.01 may one day lead to their characterization using future instruments."

The planet candidate is located a mere 33 light years from Earth and orbits its host star in only 1.4 Earth days. This star-hugging orbit means the planet would have hellish surface temperature of around 600 degrees Celsius and any atmosphere would most likely have evaporated. It is even possible that the surface could be covered in magma. 

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

The paper has been accepted for publication in The Astrophysical Journal.