Astronomers have discovered eight new planets that could potentially host life, including one that is "the most Earth-like" they have found yet.
The "incredible" findings were announced at a meeting of the American Astronomical Society in Seattle. But what makes them so significant?
What has been discovered?
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Astronomers have identified eight new alien planets that appear to orbit their parent star in the habitable 'Goldilocks' zone – a range of distances from the star where water could exist in a liquid state on the planet's surface. Scientists believe that such planets stand the best chance of supporting life.
"Most of these planets have a good chance of being rocky, like Earth," study lead author Guillermo Torres, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.
Researchers said that more work was necessary before any firm conclusions about the planets' habitability could be drawn, but that the new discoveries showed promise.
"We don't know for sure whether any of the planets in our sample are truly habitable," said co-author of the study, David Kipping. "All we can say is that they're promising candidates."
How were the planets found?
Astronomers found the planets by analysing photographs taken by Nasa's Kepler space telescope – a 4.7 metre-long spacecraft that orbits the sun every 371 days. Researchers identify new planets by looking for "transits" – the dimming of light from stars when an object travels in front of them. Scientists are then able to learn more about these planets by comparing data from other telescopes on Earth.
Are Earth-like planets rare?
So far, just 1,000 alien planets have been identified as potential worlds by the Kepler telescope, Science.com says. Of the more than 1,000 verified planets, just eight have been added to the list known as Kepler's "hall of fame", a small collection of planets that are similar in size to Earth and sit within their stars' habitable zone.
The most Earth-like of them all is one of the new discoveries announced yesterday – a planet known as Kepler 438b which is possibly "even more similar to our home than Kepler 186f – which previously looked to be our most likely twin," the BBC reports.
How similar to Earth is Kepler 438b?
The newly discovered planet is thought to be 12 per cent larger than Earth and 40 per cent hotter. It also orbits a cooler red dwarf star "so [its] sky would look redder than ours does to us," Dr Doug Caldwell from the Seti (Search for Extra-Terrestrial Intelligence) Institute in California told the BBC.
What might the planet be like?
Not much is yet known about the newly discovered planets, but according to Dr Caldwell a few assumptions can be made. "We know their size and the energy they're receiving from their star. So we can say - well, they're of a size that they're likely to be rocky, and the energy they're getting is comparable to what the Earth is getting."
However, Calwell said that the limited data means "we don't know if these planets have oceans with fish and continents with trees" but he said that continued study of the solar system would help scientists "learn more about what it means to be Earth-like".
Can we go to Kepler 438b?
Kepler 438b is 475 light years from Earth, so travelling there is presently impossible. The German-designed Helios probes, notable for having set the current speed record among spacecraft at 252,792 km/h, would take 2,029,278 years to travel to Kepler 438b. So if you would like to get there in time for tea in the year 2031293 you had better set out now.
