Astronomers last week announced that they estimate there to be 100 billion planets throughout the Milky Way Galaxy. This week, Astronomers announced 461 new candidates for extra-solar planets have been discovered.
NASA's Kepler mission has been discovering exoplanets for years now, and the number of confirmed exoplanets is currently 105. As astronomers dig more deeply into Kepler data, smaller planet candidates and multi-planet systems are becoming less rare. The new group of candidates includes four Earth-like planets that are less than twice the size of Earth and orbit their star in a region where liquid water might exist.
"There is no better way to kick off the start of the Kepler extended mission than to discover more possible outposts on the frontier of potentially life-bearing worlds," said Christopher Burke, Kepler scientist at the SETI Institute.
The number of exoplanet candidates discovered in Kepler data now sits at 2,740 planets orbiting 2,046 stars - a 20% increase from February 2012. The planet candidates are discovered by Kepler when they transit in front of their star, changing its brightness. The Kepler space telescope measures the brightness of over 150,00 stars looking for changes in their brightness. Three transits are required to declare a potential planet, and candidate data is then analyzed for known errors before follow-up observations can confirm the presence of an exoplanet.
"The analysis of increasingly longer time periods of Kepler data uncovers smaller planets in longer period orbits-- orbital periods similar to Earth's," said Steve Howell, Kepler mission project scientist at NASA's Ames Research Center. "It is no longer a question of will we find a true Earth analogue, but a question of when."
(Image courtesy NASA Ames Research Center/W. Stenzel)