Two More Alien Planets Discovered: The Smallest Ones Yet

Only one day after NASA announced the discovery of the first earth sized planets orbiting a distant star, scientists working on a different project have said they have found two even smaller alien worlds. Using the same Kepler instrument as the NASA discovery, a team of researchers focusing on another distant star found two rocky planets they weren't even looking for. The two planets are only 76% and 87% the size of Earth, and orbit their parent star in a matter of hours. That means they are far too close to their sun to have any atmosphere or liquid water.

A report debuting in the journal Nature Dec.22 will tell the tale of a star known as KIC 05807616. Scientists were watching this planet to study its inner structure by looking at its pulsing. While doing so, the team saw the tell-tale dip in the star's brightness now associated with a planet passing in front of the star, according to lead researcher Stephane Charpinet, Toulouse University, France. This is planet discovery by what's called the transit method, and the new planets have been dubbed KOI 55.01 and KOI 55.02.

Furthermore, the report will feature details about how the planets came to orbit so close to the parent star. KIC 05807616 became a red giant star, and in this stage of its life, it swelled up and engulfed the nearby planets in its outer atmosphere. This would have heated the planets to the point where any gas or atmosphere would have blown away or evaporated. The small planets were gaseous giants like Jupiter, and after their parent star blew away the atmosphere, they remained only as their inner metal cores. Because of this finding, it's unlikely the planets were ever hospitable even before their star became a red giant.