Astronomers using a NASA space telescope have discovered an alien planet smaller than Earth orbiting a star that is right on our cosmic doorstep. But the world, which is two-thirds the size of our own planet, is unlikely to be home to life – it is hotter than hell with a surface that may be covered with molten lava.
The new planet, with the uncatchy label UCF-1.01, lies just 33 light-years away in the constellation of Leo, making it one of the closest yet found outside our Solar System. It was picked up by accident by an international team using the Spitzer observatory which is in an Earth-trailing orbit around the Sun.
They were actually studying a larger planet, similar in size to our own icy giant Neptune, and orbiting a red-dwarf star called GJ 436b. But they noticed unexpected regular dips in the infrared starlight that indicated another body was passing in front of the star.
One of the scientists, Kevin Stevenson, who was at the University of Central Florida, said: “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.”
Colleague Professor Joseph Harrington and student Nate Lust, also of UCF, sifted through hundreds of hours of observations collected by Spitzer, the Deep Impact spacecraft, the Very Large Telescope (VLT) in Chile and the Canada-France-Hawaii Telescope on Hawaii to pin down more detail about the new planet.
They calculate that it is about 5,200 miles wide (8,400 km) and orbits close to its home star, zipping round it in a year lasting just 1.4 Earth days. This means the surface temperature must be more than 1,000 F (nearly 600 C). Harrington commented: “The planet could even be covered in magma.”
Harrington and Stevenson, who is now at the University of Chicago, have also found hints of a third planet, tentatively dubbed UCF-1.02, orbiting the same star but no instrument has yet been able to measure its size.
Other scientists involved in the discovery were from the University of Arizona, the European Organisation for Astronomical Research in the Southern Hemisphere, the Space Science Institute and the Southwest Research Institute. A paper about their find will appear in the Astrophysical Journal.