A "super-Earth" orbiting within the habitable zone of a star a mere 14 light years away is the closest such world ever detected, astronomers say.
Australian researchers say they found three planets orbiting the star Wolf 1061, and one of them is in the so-called "Goldilocks" zone where temperatures are just right for liquid water to exist, raising the possibility of alien life there.
Astronomers are looking closely at the middle planet — Wolf 1061c — of the trio in orbit around Wolf 1061, a small red dwarf star in the constellation Ophiuchus.
"This discovery is especially exciting because the star is extremely calm," says Duncan Wright of the University of New South Wales, lead author a study set to appear in Astrophysical Journal Letters.
"Most red dwarfs are very active, giving out X-ray bursts and super flares, which spells doom for any life, given the habitable zone is so close into these stars," he explains.
Our sun is a particularly quiet star, he notes, and Wolf 1061 is similar, suggesting its planetary system could be very old.
NASA has confirmed the existence of more than 1,800 exoplanets, but Wolf 1061c has the researchers excited because of its relative closeness to Earth.
"Other planets found that are habitable are not nearly this close to Earth," Wright says.
That should offer opportunities to study and learn more about Wolf 1061c, he notes.
The close proximity of the planets orbiting Wolf 1061 means there is a good chance for them to pass in front of the star in what is known as a transit, which would provide an opportunity to study their atmospheres to determine if they could be conducive to life, the researchers say.
"This rare discovery is incredibly exciting," Wright says. "Over the next 20 years we're going to learn a lot more about whether we're living in a galaxy with other intelligent species."
The planet, which orbits its host star every 18 days, is around 4.25 times the mass of the Earth and may be rocky in nature like our world, the researchers say.
The discovery of the three planets was made using a spectrograph on the European Southern Observatory's 3.6-meter telescope in Chile.
The star can be seen wobbling back and forth under the gravitational influence of its three orbiting words, the astronomers say.