Most of the stars in the universe are red dwarfs. Yet, SETI hasn’t paid any attention to them until now. Why? During our early search for life beyond Earth, scientists assumed we would only find it around sun-like stars. Seems reasonable. We use our planet as the analogue and look for planets with a similar planetary system.
Plus, what we know about red dwarfs doesn’t exactly inspire confidence in the search for life.
Red dwarf stars are much dimmer than stars like our sun. That means the area where planets need to orbit for life to form – the Goldilocks zone – would be much closer to the star. So close, that any planet would become tidally locked – one side always faces the star.
That’s typically bad news for any life trying to form. A red dwarf’s dimness doesn’t mean much if one side is always facing it. That side’s surface will still be scorching hot. While the night side freezes in perpetual darkness.
Ok, so red dwarfs don’t seem to be the best target for searching for life. But, there are some advantages. Red dwarf stars are old. In fact, every single red dwarf star born is still burning today. SETI Institute astronomer Seth Shostak explains why that’s a plus.
“This may be one instance in which older is better,” Shostak says. “Older solar systems have had more time to produce intelligent species.”
That’s great, but it still doesn’t solve the tidally locked problem. Recent research has a possible answer. If an exoplanet had oceans and an atmosphere, the heat on the day side could be transported to the nightside. Major portions of such a planet could support life. There’s a lot of ‘ifs’, but those ‘ifs’ don’t become certainties unless we look.
Red dwarfs aren’t the perfect solution for finding life as we know it. But outside of Earth, we can’t seem to find one. Maybe it’s time to start thinking outside the box.
Over the next two years, SETI will look at 20,000 red dwarf stars from a list of nearly 70,000. SETI Institute scientist Gerry Harp tells us what they are looking for.
The telescopes SETI uses in their search for extraterrestrial life.
“We’ll scrutinize targeted systems over several frequency bands between 1 and 10 GHz,” says Harp. “Roughly half of those bands will be at so-called ‘magic frequencies’ – places on the radio dial that are directly related to basic mathematical constants. It’s reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”
Even if we do receive a signal from one of these red dwarfs, there’s still the question of do we even respond? Plus, any stellar conversation we have would take a while. The closest red dwarf to us is Proxima Centauri at 4.25 light-years away from the Sun. That star doesn’t have any planets we know about. Most of the stars SETI will be keeping tabs on are much further away.
We might receive a signal in our lifetimes, but the conversation will play out long after we’re gone. Unless we find a Stargate. Now that would be cool.