The SETI Institute is shifting the focus of its search for extraterrestrial intelligence to places that could harbor life that’s not as we know it: 20,000 red-dwarf star systems.

“Red dwarfs – the dim bulbs of the cosmos – have received scant attention by SETI scientists in the past,” SETI Institute engineer Jon Richard said today in a news release announcing the initiative. “That’s because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the sun.”

Red dwarfs are nothing like the sun: The brightest of the breed are a tenth as luminous as the sun, and some are just 0.01 percent as bright. But astronomers say they account for three-quarters of all stars.

The star that’s closest to our sun, Proxima Centauri, is a red dwarf. A variety of observing efforts, including the Pale Red Dot initiative, are looking for planets around Proxima Centauri.

Astrobiologists had assumed that red dwarfs put out too little light to support life on alien planets, but that was before astronomers started finding Earth-sized worlds in close orbits around distant stars. Now it’s thought that 6 percent or more of all red dwarfs have potentially habitable, Earth-sized planets.

Another plus for the prospects of red-dwarf life is that such stars are amazingly long-lived: Astronomers have already detected a super-Earth known as Kapteyn b that orbits an 11.5 billion-year-old red dwarf. That makes the star and the planet 2.5 times older than Earth.]

“This may be one instance in which older is better,” SETI Institute astronomer Seth Shostak said. “Older solar systems have had more time to produce intelligent species.”

The red-dwarf search is being conducted using the institute’s Allen Telescope Array, a network of linked radio telescopes that was built amid the Cascade Mountains of Northern California using seed money from Microsoft co-founder Paul Allen.

The targets are being chosen from a list of about 70,000 red dwarfs compiled by Boston University’s Andrew West. SETI astronomers will check targeted systems over several frequency bands between 1 and 10 GHz.

“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,” SETI Institute scientist Gerry Harp said. “It’s reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”

Past searches by the SETI Institute have targeted about 1,000 nearby sunlike stars – as well as stars where NASA’s Kepler telescope detected planets, and even the oddball “alien megastructure” star known as KIC 8462852.

Although there have been some intriguing false alarms, no signals from extraterrestrial civilizations have yet been detected.