Nasa announces discovery of 'second Earth' in deep space.
Nasa has announced that it has found an extraordinarily similar planet to Earth orbiting around a distant star.
The planet, Kepler-452b, is described as a larger, older Earth and is located around a star 1,400 light years from Earth.
It is the first terrestrial planet found in the habitable zone in a star just like our sun. Nasa said it is about 60 percent larger than Earth and lies in the constellation Cygnus.
The exact nature of the planet is not known specifically, but Nasa's modelling suggesters it is a rocky planet, about five times as massive as Earth, orbiting its star once every 385 days.
The planet's star is 1.5 billion years older than our own, and is now growing hotter and brighter -- as our star will do in about a billion years.
Jon Jenkins, Kepler data analysis lead at Nasa's Ames Research Center in Moffett Field, California, said that the data showed planets similar to Earth were "common throughout the galaxy".
The planet is so similar to Earth the SETI Institute is now listening out for signals from the star Kepler 452 -- though so far it has had no luck.
"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble the Earth and our Sun," said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate at the agency’s headquarters in Washington. “This exciting result brings us one step closer to finding an Earth 2.0."
Nasa also announced that 521 new exoplanet candidates had been discovered, 12 of which have diameters between one and two times Earths, and orbit in their star's habitable zone. Nine orbit stars similar to ours in size and temperature.
Kepler, launched in 2009, looks for planets by detecting shifts in light from around 100,000 distant stars -- caused when worlds pass between our planet and the far-off sun. Finding planets of a similar size to Earth, orbiting their stars at a similar distance to our own, is extremely difficult, because it relies on the planet being positioned perfectly between its sun and ourselves, and for very small disturbances in light to be detected. Nasa compares that change in light to "the drop in brightness of a car's headlight when a fruitfly moves in front of it".
So while the 0.95m-diameter telescope has confirmed more than 1,000 planets in 440 stellar systems, and another 2,000 planet candidates, most of those worlds are either much larger than Earth or rotate too closely around their sun to harbour life.
Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago. Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamed about for thousands of years -- another Earth," a Nasa release teased on Wednesday, ahead of the news announcement.
Earlier this year Kepler found another eight new planets in the Goldilocks zone, doubling the number of exoplanets found that have a diameter less that double Earth's. "We're now closer than we've ever been for finding a twin for Earth," astronomer Fergal Mullally of the Kepler Science Office said at the time.
http://www.wired.co.uk/news/archive/2015-07/23/nasa-announces-earth-exoplanet