Astronomers have identified a record number 1,284 more planets beyond our solar system, with nine of them possibly in orbits that could be suitable for surface water, boosting the prospect of life on other planets.
The announcement brings the total number of confirmed planets outside Earth’s solar system to 3,264. Known as exoplanets, the majority of the new discoveries were made by Nasa's Kepler space telescope, which searched for habitable planets like Earth for four years from 2009 until its gyroscope-like reaction wheels failed in 2013 and Nasa engineers were obliged to abandon the mission.
The new planets identified had previously had been considered planet-candidates.
Scientists used a new analysis technique that applies statistical models to confirm the batch as planets, while ruling out scenarios that could falsely appear to be orbiting planets.
"We now know there could be more planets than stars," Paul Hertz, Nasa's astrophysics division director, said in a news release. "This knowledge informs the future missions that are needed to take us ever closer to finding out whether we are alone in the universe."
Of the new planets, Nasa believes around 550 could be rocky like Earth and nine are the appropriate distance from a star to support temperatures at which water could pool, which could in turn support living organisms. The discovery brings the total number of known planets with such conditions to 21.
Kepler looked for slight changes in the amount of light coming from about 150,000 target stars. Some of the changes were caused by orbiting planets passing across - or transiting - the face of their host stars, relative to Kepler's line of sight.
The analysis technique, developed by Princeton University astronomer Tim Morton and colleagues, analysed which changes in the amount of light are due to planets transiting and which are due to stars or other objects.
The team verified, with a more than 99 percent accuracy, that 1,284 candidates were indeed orbiting planets, Morton said.
The results suggest that more than 10 billion potentially habitable planets could exist throughout the galaxy, according to Kepler lead scientist Natalie Batalha. The nearest potentially habitable planet is approximately 11 light years from Earth.
"Astronomically speaking, that's a very close neighbor," she said.
During its mission, Kepler identified a planet that has been referred to as an older, bigger cousin of earth that shares many characteristics with our world. Known as Kepler-452b, it is more than 1,000 light years away and orbits a star similar to our Sun. It is also 60 per cent larger than Earth but lies in an orbital region where temperatures are thought to be mild enough to be suitable for life.
Since the Kepler mission was abandoned, NASA has selected a team to build a new instrument that will detect planets outside our solar system, known as exoplanets, by measuring the minuscule ‘wobbling’ of stars. The highly precise instrument will be built by a Pennsylvania State University research group with an estimated 2019 completion date.
Not to be outdone, Esa - the European Space Agency – has announced that it will build a telescope to search for habitable planets in other solar systems.
Named Plato (for Planetary Transits and Oscillations of stars), the telescope, foreseen to be launched in 2024, will work similarly to Nasa’s famous and recently retired Kepler telescope, looking for regular dips in brightness of the nearby stars as planets transit in front of them.