Another Earth just 12 light-years away?

December 19, 2012

This artist’s concept shows a generic Earth-size exoplanet in the habitable zone of a sun-like star (credit: NASA)

Astronomers have discovered what may be five planets orbiting Tau Ceti, the closest single star beyond our solar system whose temperature and luminosity nearly match the sun’s, Science Now reports.

If the planets are in fact there, one of them is about the right distance from the star to sport mild temperatures, oceans of liquid water, and even life, and slight changes in Tau Ceti’s motion through space suggest that the star may be responding to gravitational tugs from five planets that are only about two to seven times as massive as Earth.

Tau Ceti is only 12 light-years from Earth, just three times as far as our sun’s nearest stellar neighbor, Alpha Centauri.

Early SETI target

The Sun (left) is both larger and somewhat hotter than the less active Tau Ceti (right).

Tau Ceti resembles the sun so much that astronomer Frank Drake, who has long sought radio signals from possible extraterrestrial civilizations, made it his first target back in 1960. Unlike most stars, which are faint, cool, and small, Tau Ceti is a bright G-type yellow main-sequence star like the sun, a trait that only one in 25 stars boasts.

Moreover, unlike Alpha Centauri, which also harbors a G-type star and even a planet, Tau Ceti is single, so there’s no second star in the system whose gravity could yank planets away.

It’s the fourth planet — planet e — that the scientists suggest might be another life-bearing world, even though it’s about four times as massive as Earth.

If the planets exist, they orbit a star that’s about twice as old as our own, so a suitable planet has had plenty of time to develop life much more advanced than Homo sapiens.