Recently compiled estimates show that billions of worlds orbiting red dwarf-type stars in the Milky Way could meet the necessary conditions to allow for the development of basic lifeforms. The new studies significantly increase our chances of discovering life elsewhere in the Universe.
Another study has recently shown that the galaxy features around 100 billion planets, most of which probably lie around the most common type of stars, red dwarfs. Of these worlds, the vast majority may contain liquid water on their surface, experts say.
The emerging view among astronomers is that to believe we are alone is a somewhat self-centric perspective on things. Granted, the chances of finding advanced civilizations are slim, but microorganisms could easily endure on or immediately under the surface.
Compared to the Sun – which is a G-type yellow dwarf – red dwarfs are smaller, cooler, and fainter. Their habitable zones are a lot closer to the stellar surface as well, since the object provides less heat and light than the Sun does. On the other hand, they account for 80 percent of stars in the galaxy.
“The habitable zone would be very, very small. Consequently, the chances that you would actually find any planet at the right distance from the sun to be attractive to life was likely to be small, too,” explains Search for Extraterrestrial Intelligence (SETI) Institute senior astronomer, Seth Shostak.
However, the latest research on the issue, carried out using the HARPS spectrograph in Chile, demonstrates that around 41 percent of all red dwarfs may host extrasolar planets inside their habitable zones. The study was carried out on a sample of 102 red dwarfs.
“The number of habitats might increase by a factor of 8 or 10,” Shostak explained in an interview for Space
. He added that radiation is the main problem on these worlds, given their proximity to their parent stars. However, a strong magnetosphere such as our own may provide a lot of protection.
Oceans of liquid water would also offer protection from harmful radiation, allowing organisms to develop under the sea. If this is the case, then the radio antennas SETI uses to listen in on the night sky may not pick up any signals any time soon.
“We're not sure intelligent life, if under water, will be building radio transmitters and we're going to hear from them. But it's possible,” Shostak said. An additional problem, he continued, is tidal locking.
This phenomenon can be seen between the Earth and the Moon. Our natural satellite is tidally locked to the planet due to Earth's intense gravitational pull, and cannot rotate around its own axis.
When a planet is tidally locked to its star, it always keeps the same face pointed towards the latter, therefore exhibiting permanent daysides and nightsides. The difference between temperatures on the two sides would be staggering, researchers say.