Milky Way may boast billions of habitable planets

Milky Way may contain billions of habitable planets The Milky Way may be teeming with billions of habitable planets, according to a recent survey – and that’s given the search for extra-terrestrial life a big boost. Two Princeton researchers recently speculated that we really might be alone in the universe, but the study of red dwarf stars in the Milky Way found nine super-Earths - and two in the 'habitable zone' where liquid water could exist.
Red dwarf stars account for 80 per cent of the 200 to 400 billion stars in our galaxy - and scientists now believe that 40 per cent of those might have a planet in the habitable zone.
This is great news for the alien hunters at the California-based SETI institute - the Search for Extraterrestrial Intelligence.
SETI Senior Astronomer Seth Shostak told Space.com: ‘SETI is looking for Mr. Right or maybe Ms. Right, depending on your point of view. It helps to find out that there's 10 times as many candidates as there were before.’
Shostak warns, however, that because red dwarfs are relatively dim, planets would need to orbit very close to them to get enough heat for life to grow, which would mean they’d receive potentially fatal doses of radiation.
Protection may exist, though, in the form of a magnetic field around the planet – or large oceans, which would shield aquatic life.
‘We're not sure intelligent life, if under water, will be building radio transmitters and we're going to hear from them,’ Shostak added. ‘But it's possible.’
The revelation that the Milky Way may be crammed with habitable planets came from an international team of star gazers led by Dr Xavier Bonfils, from Grenoble University in France.
He said: ‘Because red dwarfs are so common - there are about 160 billion of them in the Milky Way - this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone.’
The astronomers surveyed a carefully chosen sample of 102 red dwarfs using the European Southern Observatory's 3.6-metre telescope at La Silla, Chile.
A total of nine super-Earths - planets with masses between one and 10 times that of Earth - were found.
Two were located within the habitable zones of the stars Gliese 581 and Gliese 667 C.
These data were combined with other observations, including those of stars which did not have planets.
The astronomers worked out that habitable zone super-Earths orbiting red dwarfs occurred with a frequency of around 41 per cent.
On the other hand massive planets similar to Jupiter and Saturn were rare around red dwarfs. Less than 12 per cent of the stars were expected to have such ‘gas giants’.
Because red dwarfs are common near the sun, many ‘super-Earths’ may not be far away in astronomical terms.
The scientists estimate there could be around 100 habitable zone planets within 30 light years.
The research was reported in the journal Astronomy & Astrophysics.