Credit | NASA

NASA's Kepler space telescope has discovered an Earth-like planet that scientists say is capable of supporting life. Kepler-22b is, according to NASA, an extra-solar planet, meaning it exists outside of our solar system, the Milky Way.

From CNET:

It is not yet known whether Kepler-22b is predominantly rocky, liquid, or gaseous in composition, but the finding confirms for the first time the long-held expectation that Earth-size planets do, in fact, orbit other suns in the habitable zones of their host stars.

That, in turn, greatly improves the odds for the existence of life, as it is commonly defined, beyond Earth's solar system.

"I think there are two things that are really exciting about Kepler-22b," said Natalie Batalha, the deputy science team lead at Ames. "One is that it's right in the middle of this habitable zone.

"The second thing that's really exciting is it's orbiting a star very, very similar to our own sun. This is a solar analogue, almost a solar twin, very similar to our own sun and you've got a planet 2.4 times the size of the Earth right smack in the habitable zone.

One of the main criteria Kepler-22b meets for being a habitable planet is its temperature, which has been observed to be fairly moderate when compared to Earthly standards.

From the UK Telegraph:

This range of ideal temperatures is known to scientists as the “Goldilocks” zone, as the temperature is “just right” for life.

Bill Borucki, Kepler principal investigator at NASA Ames Research Centre, said: “We have now got good planet confirmation with Kepler 22b.
“We are certain that it is in the habitable zone and if it has a surface it ought to have a nice temperature.”

There are now three planets outside the system, known as exoplanets, which experts believe could potentially be colonised by future generations.

In May, French astronomers identified Gliese 581d, pronounced “gleezer”, which is far closer at around 20 light years away.
It is about six times the mass of Earth and is one of a family of at least six planets.

In August, a team from Switzerland reported that another planet called HD 85512b and 36 light years away seemed to be habitable.

Now, scientists have said up to three years of observation is needed to confirm anything further.