Earth is one unique planet among the rest of the planets scattering across the universe. It is the only known planet which liquid water is abundant and numerous living organisms inhabit. However, Earth may no longer be as unique as we think it is.
The Kepler mission‘s science team has found a planet that is similar to Earth which locates in the “habitable zone” of its solar system. A habitable zone is a region around a sun where water can maintain its liquid state on a planet with sufficient atmospheric pressure. 600 light years from Earth, Kepler-22b, a planet which orbits in Kepler-22 system, has a radius 2.4 times the radius of Earth and an orbit period about 290 days. Its star, Kepler-22, is slightly smaller and cooler than our Sun. The composition of Kepler-22b is not yet determined by the Kepler Science team. However, judging from the size of Kepler-22b, the team estimated that the composition of Kepler-22b is most likely to be similar to earth composition with abundant amount of water.
(Artist’s concept of Kepler-22b from Kepler: Home Page)
How did Kepler science team find Kepler-22b which is 600 light years from Earth? The science team used Kepler telescope, which can monitors the slight decrease in brightness of stars when a planet orbits across the star. Kepler telescope can detect the change in brightness up to one ten-thousandth difference. Based on the amount of brightness decreased, the team can determine the size of the planet. In order to confirm the change in the brightness of a star is caused by a planet orbiting across the star, the team has to find 3 dips of brightness. These dips are separated with a set period of time to confirm the orbital period of the planet.
Although Kepler-22b is the first confirmed Earth-like planet which orbits in the “habitable zone” of its system, there are total of 48 possible planet candidates that are being observed by the Kepler mission’s science team. There is little doubt that more Earth-like planets will be discovered by the Kepler mission. Perhaps, within these planet candidates, there may be life living on one of these Earth-like planets.
References:
Media announcement of NASA’s Kepler mission’s science team on December 5th,2011:
https://www.youtube.com/watch?v=en5OObU0ryU
Article of discovery of Kepler from NASA website:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-373
Kepler Mission: Home Page
Kelper-22b From NASA Kepler website:
http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=165
Artist’s concept of Kepler-22b
http://kepler.nasa.gov/images/Kepler22bArtwork.jpg
