Scientists have announced the discovery of new planets that are likely to support life similar to our own planet, Earth.  One of the most promising candidates is actually closer than you might think, located only 470 light-years away.

The new exoplanets (planets located outside our solar system) have been discovered by analysis of data from the Kepler space telescope.  Eight new planets were discovered with two in particular, designated Kepler-438b and Kepler-442b showing the most promise; though Kepler-438b is the most hospitable for life of the planets.

Both planets orbit red dwarf stars, which are smaller and less hot when compared to our Sun.  Kepler-438b has a 35 Earth day year, with Kepler-442b's year lasting 112 Earth days.  With a diameter only 12 percent larger than the Earth, Kepler-438b has a 70 percent chance of being rocky, according to calculations.  Kepler-442b, on the other hand, is approximately one-third larger than the Earth, but still has a 60 percent chance of being rocky.

Kepler-438b gets about 40 percent more heat from its red sun compared to the Earth, and scientists believe there is roughly a 70 percent chance that liquid water could exist on the surface.  The presence of water is generally thought to be the basic requirement for the appearance of life, or for it to be potentially habitable by humans.  This assumes that a biosphere is present, providing atmospheric oxygen.

Kepler-442b, on the other hand, receives about two-thirds as much light as Earth and is believed to have a 97 percent chance that water could exist on the surface.  This planet is located 1,100 light-years from the Earth, putting in a bit farther away compared to Kepler-438b, which is only 470 light-years away from us.

"We don't know for sure whether any of the planets in our sample are truly habitable," astronomer David Kipping says. "All we can say is that they're promising candidates."

These planets were too small to be identified by a mass measurement.  So in order to better determine not only their size, but also their qualities, researchers had to use other methods with which they sized-up the eight new candidates.

"All of the planets were too small to confirm by measuring their masses" NASA spokespersons say. "Instead, the team validated them by using a computer program called BLENDER to determine that they are statistically likely to be planets. BLENDER runs on the Pleaides supercomputer at NASA Ames. This is the same method that has been used previously to validate some of Kepler's most iconic finds, including the first two Earth-size planets around a Sun-like star and the first exoplanet smaller than Mercury."

"Kepler collected data for four years - long enough that we can now tease out the Earth-size candidates in one Earth-year orbits" says SETI astronomer Fergal Mullally of the Ames campus. "We're closer than we've ever been to finding Earth twins around other sun-like stars. [And] these are the planets we're looking for."