1,200 Light-Years Away, a Planet That Could Harbour Life

A planet which is about 1,200 light-years from Earth and in all probabilities has surface liquid water is a good prospect for a habitable world, reports researchers from University of California-Los Angeles.

Named Kepler-62f, the planet is situated in the direction of the constellation Lyra and is approximately 40 percent larger than Earth.

"At that size, Kepler-62f is within the range of planets that are likely to be rocky and possibly could have oceans," said Aomawa Shields, lead author and a astrophysics postdoctoral fellow.

Nasa's Kepler mission discovered the planetary system that includes Kepler-62f in 2013 and it identified Kepler-62f as the outermost of five planets orbiting a star that is smaller and cooler than the Sun.

But the mission did not reveal information about its composition or atmosphere or the shape of its orbit.

To determine whether the planet could sustain life, the team came up with possible scenarios about what its atmosphere might be like and what the shape of its orbit might be.

"We found there are multiple atmospheric compositions that allow it to be warm enough to have surface liquid water. This makes it a strong candidate for a habitable planet," added Shields.

On Earth, carbon dioxide makes up 0.04 percent of the atmosphere.

Because Kepler-62f is much farther away from its star than Earth is from the Sun, it would need to have dramatically more carbon dioxide to be warm enough to maintain liquid water on its surface, and to keep from freezing.

The team ran computer simulations and found many scenarios that allow it to be habitable, assuming different amounts of carbon dioxide in its atmosphere.

Shields said that for the planet to be consistently habitable throughout its entire year, it would require an atmosphere that is three to five times thicker than Earth's and composed entirely of carbon dioxide.

Having such a high concentration of carbon dioxide would be possible for the planet because, given how far it is from its star, the gas could build up in the planet's atmosphere as temperatures get colder to keep the planet warm.

The scientists made their calculations of the shape of the planet's possible orbital path using an existing computer model called HNBody.

The research was published online in the journal Astrobiology.

According to Shields, the same technique could be applied to understand whether exoplanets much closer to Earth could be habitable, so long as the planets are likely to be rocky.

"This will help us understand how likely certain planets are to be habitable over a wide range of factors, for which we don't yet have data from telescopes," she noted.

More than 2,300 exoplanets have been confirmed so far and a few thousand others are considered planet candidates, but only a couple dozen are known to be in the "habitable zone".