Telescope confirms three new ‘Earth-like’ planets

Three new planets, roughly the size of Earth, have been found in the ‘not too hot, not too cold — just right’ zone around their stars, significantly boosting the numbers of potentially habitable worlds.

And one of them may potentially be the most Earth-like yet discovered.

NASA’s Kepler mission early this morning made the announcement at a presentation marking the discovery of its 1000th exoplanet — the name given to worlds found orbiting stars other than our own. The results will soon be published in The Astrophysical Journal.

In addition to the three verified potentially habitable worlds, there are unconfirmed traces of a further six in orbits potentially capable of sustaining life.

“With each new discovery of these small, possibly rocky worlds, our confidence strengthens in the determination of the true frequency of planets like Earth,” study co-author Doug Caldwell, SETI Institute Kepler scientist said in a statement. “The day is on the horizon when we’ll know how common temperate, rocky planets like Earth are.”

The three new worlds judged to be in the “Goldilocks zone” bring the total of potentially life-sustaining worlds to about 24 — eight of which have been found by Kepler. It’s a tally that has gradually been picking up pace since the first exoplanet was detected in 1992.

The now technically-challenged Kepler telescope has had to undergo some emergency innovation and adaptation after experiencing difficulties a year ago, but it continues to produce results.

The latest figures reveal the telescope has continued to closely monitor some 150,000 stars for the telltale “wobble” in their light that could be the shadow of a passing planet.

More than 4000 such ‘wobbles’ have been determined by the Kepler team as potential planetary candidates. 1000 of these are now judged as certainties.

When the results of other planet-hunting telescopes are included, space is starting to look somewhat crowded.

The NASA announcement states that two of these new worlds are believed to be made up of rock, like Earth.

“Each result from the planet-hunting Kepler mission’s treasure trove of data takes us another step closer to answering the question of whether we are alone in the

Universe,” said John Grunsfeld, associate administrator of NASA’s Science Mission.

It’s not an easy task, given the immense distances involved.

To judge a planets potential for life, scientists must first determine if it is mad of gas, ice or rock. To do this they must find out both its size and weight. The resulting mass is a good indicator of a planet’s composition.

If its weight cannot be determined, size does provide some indication: Huge worlds are almost always gas. Tiny worlds (such as Earth) are almost always rock.

The Kepler announcement says two of the new validated planets, Kepler-438b and Kepler-442b, are less than 1.5 times the diameter of Earth. This means their gravity and potential atmospheres are likely to be within an acceptable range for life as we know it.

Kepler-438b, some 475 light-years away, is 12 per cent bigger than Earth and orbits its star once every 35.2 days. It’s getting about 40 per cent more heat than we do from its orange dwarf star. At this size, and in this location, this world appears to be the most likely candidate for a ‘habitable’ planet yet found.

Kepler-442b, 1,100 light-years away, is 33 per cent bigger than Earth and orbits its star once every 112 days. It is also one of the few worlds sitting in the narrow range of weight, size and orbital distance to make it ‘just right’ for life.

Both planets orbit stars much smaller and cooler than ours, meaning their fast orbits are still within a temperate region which can sustain liquid water.

Both stars are in the direction of the constellation Lyra.

Hubble has added 554 more ‘wobbles’ in starlight to the list of potential planets — bringing the total number of unconfirmed candidates to 4175.

Six of these candidates are reportedly showing signs of being between one and two times the size of Earth, and in warm, water-sustaining orbits around stars similar to our own. But further observations are needed before their presence, size and location can confirmed.

“Kepler collected data for four years — long enough that we can now tease out the Earth-size candidates in one Earth-year orbits”, said Fergal Mullally, a SETI Institute Kepler scientist.

“We’re closer than we’ve ever been to finding Earth twins around other sun-like stars. These are the planets we’re looking for”.