— A newly found planet is at least 4.5 times bigger than Earth
— The planet circles its star in 28.15 days, but the star is dimmer than the sun so it could host liquid surface water.
— The planet gets mostly infrared light, so processes like photosynthesis, if it exists, would be different than on Earth.
Scientists have discovered a planet about five times bigger than Earth flying the right distance from its parent star for liquid water to exist on its surface, a condition believed to be necessary for life.
The newly found planet circles a star dimmer than the sun that is located 22 light-years away in the constellation Scorpius (also known as Scorpio.) It passes around its parent star in 28.15 days.
While far closer to its star than Earth is to the sun, the planet's parent star, known as GJ 667C, is a small dwarf star that emits most of its light in infrared radiation. That means GJ 667C's so-called "habitable zone" — the region where surface water can exist in liquid form — is closer than our sun's region.
Scientists don't know if the newly discovered world, called GJ 667Cc, is solid or not.
"It is possible to determine, but we have to be lucky. The planet would have to transit in front of the star. We haven't checked yet if that happens," lead researcher Guillem Anglada-Escudé, formerly with the Carnegie Institution for Science, told Discovery News.
GJ 667Cc was discovered after Anglada-Escudé and his team rechecked data collected by a rival planet-hunting group in Europe called HARPS.
That team earlier announced a discovery of a super-Earth around the same star, but one that orbits in just 7.2 days — too close to be in the star's habitable zone.
Anglada-Escudé and colleagues developed new software to recheck that planet's orbital information and came up with its more fortuitously positioned sibling. The system also may include a gas-giant planet and a third super-Earth with an orbital period of 75 days.
The planets were found with a technique that measures small wobbles in a star's orbit caused by the gravitational tug of orbiting planets.
The planets orbit a star that is partnered with a pair of metal-poor binary stars. Previously, scientists didn't believe such stars would have the right building blocks for planets.
If there is any life on GJ 667Cc, it likely would be very different from what is found on Earth. Rather than yellow star, GJ 667Cc's sun is red.
"It doesn't receive as much light as Earth," Anglada-Escudé said, adding that if the planet had an atmosphere, conditions would be prime for greenhouse gas production.
It also would make for interesting conditions for photosynthesis, if any exists.
The research appears in this week's Astrophysical Journal Letters.