NASA's Kepler space telescope, in an Earth trailing Solar Orbit, designated Kepler-11 about two thousand light years from Earth.
Five of the planets, ranging from 2.3 to 13.5 times the mass of the Earth, are orbiting Kepler-11 in a tight orbit that has a period of only about fifty days, closer to the their star than Mercury is to the Sun. The sixth planet is larger and farther out with an orbital period of 118 days and has a mass yet to be determined.
The Kepler space telescope's mission is to find Earth-like planets orbiting other stars, which would be about the same size and mass as the Earth with an orbit around a star similar to the Sun in the "zone of habitability", far enough out to not be too warm, but not so far as to be too cold. While Kepler has been, it has yet to discover another Earth. The discovery at Kepler-11 comes close and is, in itself, scientifically significant.
The Kepler detects planets by measuring the slight decrease in a star's brightness when a planet transits in front. The size is determined by the amount of decrease. The orbital period is determined by the time between transits.
Usually when a new planet is discovered, its mass is measured with Doppler spectroscopy which determines the amount of star's wobble that the gravitational pull of the planet causes. But Kepler-11 is too far away and the planets too small to use this method. Instead scientists measured the variations of the orbital periods caused by gravitational interactions among the planets.
Most new planets that have been discovered orbiting other stars have been gas giants, some of them much larger than Jupiter, the largest planet in our solar system, and mostly just one planet per star. The Kepler-11 discovery is remarkable in the number, size, and orbits of the newly discovered planets. Though none of Kepler-11's world could sustain life (at least as we know it) the discovery will allow scientists to study the interactions of a multi planet solar system, other than our own, for the first time in history.
The Kepler-11 discovery, while remarkable, is still short of the hoped filled detection of an Earth-like world orbiting another star. When that happens, whether it is on the Kepler mission or by some other means, the perception of humankind's role in the universe will change. Other Earth-like planets have been a staple of science fiction for many decades and scientists, simply by the law of averages, believe that other Earths exist. But the confirmation of one would be the most significant scientific discovery of this century so far.
CREDIT : Mark Whittington,Yahoo Contributors Network
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals
