NASA’s Kepler mission has successfully discovered over a thousand planets since its launch just over a year ago. Of those, around 70 are Earth-sized and 50 may be in the habitable zone (the proper distance from the sun for liquid water). To add to that, the Kepler space telescope recently discovered a complete ‘solar’ system around a distant star.
In Kepler-11, located 2000 light years from Earth, researchers have discovered the first star system to contain more than three planets. Kepler-11 has at least six planets, creatively named Kepler-11a through 11g. All are considerably larger than the Earth, and considerably closer to their star than the Earth is to the sun. The furthest out of the six, Kepler-11g, is only half as far away from its sun as the Earth is from the sun, and the other five orbit closer than Mercury does to the sun.
This artist's conception shows the Kepler-11 planetary system and our solar system from a tilted perspective to demonstrate that the orbits of each lie on similar planes.Credit: NASA/Tim Pyle.
The planets were discovered using the ‘transit method’. For this technique to work, the planets must cross in front of their star from the perspective of the telescope. The miniscule drop in light caused by this transit yields information about the size of the planet and its orbit velocity. The six Kepler-11 planets appear to be rocky, though not in the habitable zone.You can read a lot more about this extrasolar system on Phil Plait’s blog, Bad Astronomy.