The SETI Institute in California plans to expand the hunt for radio signals transmitted by extraterrestrial civilizations by scanning red dwarf stars that are older and smaller than stars like the Sun.
The shift stems from the recent discovery that red dwarfs, which are by far the most common type of star, can and have planets in orbit that are in the correct position to maintain liquid water on the surface, a condition considered to be a key factor for life.
Planets in the so-called “habitable zones” of red dwarfs would have an orbit much closer than the Earth’s orbit around the Sun, because red dwarfs are much smaller and colder Sun. Scientists have previously believed that close orbits mean that any planets will be tidal blocked by their parent stars, with half the planet burning hot and the other half in constant darkness and cold.
But a new study shows that if the planets had oceans and atmosphere, then the heat from their parent red dwarfs would be distributed more evenly. "A significant part of the planet may be habitable," the SETI astronomers said in a press release.
The presence of 75 percent of all stars classified as red dwarfs means that the hunt for aliens can take place closer to Earth, where potential signals will be stronger.
"If you watch the next 20,000 (red dwarf stars), then on average they will be only half a distance away from the closest of 20,000 stars like the Sun," SETI astronomer Seth Shostak said.
In addition, since the red dwarfs of ancient stars are billions of years older than stars like the Sun, life on them would have more time to develop.
"The old solar systems had more time to produce a reasonable view," said Shostak.
The search, which will target 20,000 selected targets and will take about two years, is conducted on the Allen Telescope Array at the SETI Institute, located in the Cascade Mountains of northern California.