Planet ‘like Earth’ is in habitable zone

NASA’S planet-hunting space telescope Kepler has discovered what may be the most Earthlike world yet found in the galaxy – with temperatures favourable for alien life. Its diameter is about 2.4 times that of our own planet and it orbits a star like the Sun 600 light-years away in the Milky Way.

A NASA artist's conception of Kepler-22b
A NASA artist's conception of Kepler-22b (Credit: NASA/Ames/JPL-Caltech)

Importantly the planet, labelled Kepler-22b, lies inside the Goldilocks zone of its solar system, so-called because it is not to hot and not too cold for liquid water – an essential requirement for life as we know it. It has a year 290 days long, which is how long it takes to orbit its own parent star.

Scientists cannot tell for sure yet whether Kepler-22b is a rocky world, a gas ball or even a liquid object. But its discovery, announced this week at a conference in the US, suggests once again that Earth is not unique in hosting life in the galaxy – indeed the universe may even be teeming with alien life.

The Kepler mission, launched in March 2009, has discovered more than 2,000 of candidates for new planets in the small patch of sky it is scanning. It discovers its new worlds by watching for a blink in starlight as one passes directly in front of its home star.

The NASA team uses other telescopes to review its discoveries and check their existence. Of those proved to be there, 22b is the first Earthlike world to be confirmed to lie in that vital habitable zone. More small worlds are expected to be found by the remarkable Kepler mission.

Other observatories around the world and in space have also been finding hundreds of what are known as extrasolar planets. The vast majority discovered have been hot giant gas worlds like Jupiter and so unsuitable for life as we know it. But Kepler is finding more and more smaller planets, closer in size to Earth, and suggesting that solar systems may be commonplace in space. A NASA report has itself concluded that there could be rocky planets galore in our galaxy.

Astronomers have discovered organic molecules – the building blocks for life – developing in clouds of gas and dust that are cosmic nurseries where new stars and planets are being born. These ingredients from which every one of us was made have been found inside comets and meteorites that bombarded the Earth, and our sister planets, over billions of years.

Together with the Kepler results it points to the exciting possibility that aliens really out there – even if they are only simple bugs. Missions to Mars, such as Curiosity which is on its way there now, are trying to find out if it might have been home to life. It is now clear that much of the planet was once under water. Plumes of methane have been detected whch could conceivably be being produced by living organisms beneath the martian surface today.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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