KELPER TELESCOPE.
http://www.scientificamerican.com/extraterrestrial-life/
Since rocketing into space in 2009, NASA’s planet-hunting Kepler space telescope has discovered more than 4,500 confirmed or candidate worlds, in the process reshaping our entire view of the prospects for life in the universe. Thanks to Kepler, we can now conjecture that planets circle essentially every star in the sky, perhaps 10 percent of those might be habitable, and our solar system’s familiar architecture of small inner worlds and outer giants is rather rare in the cosmos.
And yet despite all these revolutionary results, Kepler’s most sought-after quarry—a mirror Earth around another sunlike star—has proved elusive. At least, that is, until now. At a NASA press conference today that also unveiled more than 500 other new candidate planets, Kepler’s mission scientists announced they have finally found and confirmed what looks to be the mission’s long-sought holy grail, a near-twin of Earth called Kepler 452 b. The discovery is detailed in a paper to be published in The Astronomical Journal. “Yes, this is the first small, possibly rocky planet in the habitable zone of a sunlike star,” says lead author Jon Jenkins, an astronomer and 20-year veteran of the Kepler mission at the NASA Ames Research Center. Kepler 452 b is estimated to be 1.6 times the size of our own world, and resides in a clement, life-friendly orbit around a star in the constellation of Cygnus some 1,400 light-years away that is eerily similar to our own sun.
The discovery marks the end of a long road. Before reaching the launch pad, Kepler endured decades of developmental woes as its advocates struggled to convince NASA the mission would actually work as planned. After Kepler finally launched, the setbacks continued. Most of the sunlike stars it surveyed for planets proved to be far less placid than our own star, contaminating the spacecraft’s delicate datasets with astrophysical “noise” that would require years of extra observing time to overcome. Even worse, the reaction wheels used to point the spacecraft wore out earlier than planned, bringing the primary mission to a premature end in 2013.
Early in its mission, Kepler managed to find some tantalizing worlds, a handful of supersize cousins of Earth, most of them in clement orbits around smaller, cooler, quieter stars than the sun called M and K dwarfs, but all the setbacks made finding smaller Earth-sized planets around sun-like G stars a very tall order. “We thought perhaps that our hopes of finding small, rocky habitable worlds orbiting sunlike stars were dashed,” Jenkins recalls. But thanks to a host of ingenious analytic techniques and observation methods developed on the fly, with each new pass through Kepler’s data mission scientists have managed to wring out ever-smaller planets. And as those smaller, cooler planets pile up, astronomers are coming ever closer to pinning down the number of potentially habitable, potentially Earth-like planets in our galaxy, a value they call “eta-Earth.”
“We’re watching Kepler zero in on the Earth analogues in slow motion,” says study co-author Natalie Batalha, an astrophysicist at Ames who is also Kepler’s mission scientist. “The closer we get, the harder it gets. We’re tromping through the weeds, looking for the most precious stones…. Some said Kepler couldn’t find small habitable-zone planets orbiting G-type stars. Now that we have, I’m confident that Kepler will determine eta-Earth not just for K and M stars but also for G stars.” Knowing eta-Earth, Batalha says, will allow astronomers to estimate how nearby the closest Earth twins are and thus how large future space telescopes will have to be to image those planets and study them for signs of life.
After today’s data release, however, there will be only one more official Kepler release sometime next year. Although astronomers hope to wrest further discoveries from the mission’s archives for generations to come, the end is near for Kepler’s hunt for habitable worlds. “We are reaching the limit of what the Kepler project has to offer regarding the prevalence of potentially Earth-like planets,” says Kepler team member Joe Twicken, an astronomer and study co-author at the SETI Institute.
