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Kepler telescope bags huge haul of planets Kepler telescope bags huge haul of planets
(35 minutes later)
The science team sifting data from Nasa's Kepler space telescope says it has identified 715 new planets beyond our Solar System.The science team sifting data from Nasa's Kepler space telescope says it has identified 715 new planets beyond our Solar System.
This is a huge new haul.This is a huge new haul.
In the nearly two decades since the first so-called exoplanet was first discovered, researchers had claimed the detection of just over 1,000 new worlds. In the nearly two decades since the first so-called exoplanet was discovered, researchers had claimed the detection of just over 1,000 new worlds.
Kepler's latest bounty orbit only 305 stars, meaning they are in multi-planet systems. Kepler's latest bounty orbit only 305 stars, meaning they are all in multi-planet systems.
The vast majority, 95%, are smaller than our Neptune, which is four times the radius of the Earth.The vast majority, 95%, are smaller than our Neptune, which is four times the radius of the Earth.
Four of the new planets are less than 2.5 times the size of Earth, and they orbit their host suns in the "habitable zone" - the region around a star where water can keep a liquid state. Four of the new planets are less than 2.5 times the radius of Earth, and they orbit their host suns in the "habitable zone" - the region around a star where water can keep a liquid state.
Whether that is the case on these planets cannot be known for sure - Kepler's targets are hundreds of light-years in the distance. This is too far away for very detailed investigation. Whether that is the case on these planets cannot be known for sure - Kepler's targets are hundreds of light-years in the distance, and this is too far away for very detailed investigation.
Kepler was launched in 2009 on a $600m (£395m) mission to assess the likely population of Earth-sized planets in our Milky Way Galaxy. Kepler was launched in 2009 on a $600m (£360m) mission to assess the likely population of Earth-sized planets in our Milky Way Galaxy.
Faulty pointing mechanisms eventually blunted its abilities last year, but not before it had identified thousands of possible, or candidate, worlds in a small patch of sky in the Constellation Lyra. Faulty pointing mechanisms eventually blunted its abilities last year, but not before it had identified thousands of possible, or "candidate", worlds in a small patch of sky in the Constellation Lyra.
It did this by detecting the periodic variations in the brightness of stars caused by orbiting exoplanets passing in front of them. It did this by looking for transits - the periodic dips in light that occur when planets move across the faces of stars.
Douglas Hudgins from Nasa's astrophysics division summed up the significance of the latest news: "This is the largest windfall of planets that's ever been announced at one time. Second, these results establish that planetary systems with multiple planets around one star, like our own Solar System, are in fact common. Of something like 3,600 candidates recorded, just over 20% have now been moved up to the status of confirmed detections by the Kepler team.
"This is the largest windfall of planets that's ever been announced at one time," said Douglas Hudgins from Nasa's astrophysics division.
"Second, these results establish that planetary systems with multiple planets around one star, like our own Solar System, are in fact common.
"Third, we know that small planets - planets ranging from the size of Neptune down to the size of the Earth - make up the majority of planets in our galaxy.""Third, we know that small planets - planets ranging from the size of Neptune down to the size of the Earth - make up the majority of planets in our galaxy."
One analysis of Kepler data published in November suggested that perhaps one in five stars like our Sun hosts an Earth-sized world located in the habitable zone. When Kepler first started its work, the number of confirmed planets came at a trickle.
Scientists had to be sure that the variations in brightness being observed were indeed caused by transiting planets and not by a couple of stars orbiting and eclipsing each other.
The follow-up work required to make this distinction - between candidate and confirmation - was laborious.
But the sudden dump of new planets announced on Wednesday has exploited a new statistical approach referred to as "verification by multiplicity".
This rests on the recognition that if a star displays multiple dips in light, it must be planets that are responsible because it is very difficult for several stars to orbit each other in a similar way and maintain a stable configuration.
"This technique that we've introduced for wholesale planet validation will be productive in the future. These results are based on the first two years of Kepler observations and with each additional year, we'll be able to bring in a few hundred more planets," explained Jack Lissauer, a planetary scientist at Nasa's Ames Research Center.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmosJonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos