World

Nasa discovers Earth-like planet in ‘habitable zone’

The planet which is about 60% bigger than Earth is located 1,400 light years away

An artist’s impression compares Earth (left) to the new planet, called Kepler-452b, which is about 60 per cent larger in diameter. Photograph: Nasa/JPL-Caltech/T. Pyle
An artist’s impression compares Earth (left) to the new planet, called Kepler-452b, which is about 60 per cent larger in diameter. Photograph: Nasa/JPL-Caltech/T. Pyle
Thu Jul 23 2015 - 18:50

Nasa says it has discovered an earth-like planet in a "habitable zone" around a star similar to the sun.

Scientists using Nasa’s powerful Kepler telescope have found a planet beyond the solar system that is a close match to Earth.

The planet, which is about 60 per cent bigger than Earth, is located about 1,400 light years away in the constellation Cygnus, the scientists told a news conference on Thursday.

Highlighted (yellow open circles) are 12 new planet candidates from the seventh Kepler planet candidate catalog that are less than twice the size of Earth and orbit in the stars’ habitable zone – the range of distances from a star where liquid water could exist on the surface of an orbiting planet. The dark green area represents an optimistic estimate for the habitable zone, while the light green area represents a more conservative estimate for the habitable zone. Photograph: Nasa Ames/W. Stenzel
Highlighted (yellow open circles) are 12 new planet candidates from the seventh Kepler planet candidate catalog that are less than twice the size of Earth and orbit in the stars’ habitable zone – the range of distances from a star where liquid water could exist on the surface of an orbiting planet. The dark green area represents an optimistic estimate for the habitable zone, while the light green area represents a more conservative estimate for the habitable zone. Photograph: Nasa Ames/W. Stenzel
The new world orbits at roughly the same distance from its sun as Earth does. Photograph: Nasa/JPL-Caltech/T. Pyle
The new world orbits at roughly the same distance from its sun as Earth does. Photograph: Nasa/JPL-Caltech/T. Pyle

While similarly sized planets have been found before, the latest one, known as Kepler-452b, is circling a star that is very similar but older than the sun at a distance about the same as Earth’s orbit.

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“It’s great progress in finding a planet like Earth that is similar in size and temperature around a sun-like star,” Jeff Coughlin, Kepler research scientist at the SETI Institute in Mountain View, California, told reporters on a conference call.

Based on its size, scientists believe Kepler-452b is rocky and Earth-like and positioned at the right distance for liquid surface water.

The research will be published in an upcoming issue of The Astronomical Journal.

Kepler-452b’s orbit around its sun-like star takes 385 days, just slightly longer than our own year, putting it firmly in the “Goldilocks” habitable zone where the temperatures are lukewarm and suitable for liquid water on the surface – if it has a surface.

The planet’s size is right on the hairy edge between being rocky like Earth and being a fluffy gas ball like Neptune, according to studies of other such exoplanets.

In an email, Jon Jenkins, an astronomer at Nasa’s Ames Research Center, home of the Kepler project, and lead author of a paper being published in The Astronomical Journal, said the planet had between a 50 per cent chance and a 62 per cent chance of being rocky, depending on uncertainties in the size of its home star. That would mean its mass is about five times that of Earth.

To determine whether Kepler-452b deserves a place on the honor roll of possible home worlds, astronomers have to measure its mass, which requires being close enough to observe the wobbling of the star as it is tugged around by the planet’s gravity. For now that is impossible, as Kepler-452 is 1,400 light-years away.

The planet is the first to be confirmed in a new list of candidates unveiled by Kepler astronomers. It brings the list of possible planets discovered by Kepler to 4,675. The spacecraft, launched in 2009, spent four years staring at a patch of the Milky Way on the border between the constellations Cygnus and Lyra, looking for the dips in starlight caused by planets passing in front of their stars.

Its pointing system failed in 2013, but astronomers are still analysing the data Kepler collected. Every time they sift through the data, new planets pop out. In the meantime, Kepler has switched to a different mode of observing in a new mission they call K2.

Astronomers say they now know from Kepler that about 10 per cent of the 200 billion stars in the Milky Way have potentially habitable Earth-size planets, Kepler-452b probably among them. This means that of the 600 stars within 30 light-years of Earth, there are roughly 60 E.T.-class abodes, planets that could be inspected by a future generation of telescopes.

Reuters/New York Times