"This is the first time that we have detected water on a planet in the habitable zone around a star where the temperature is potentially compatible with the presence of life," said lead author, the physicist Giovanna Tinetti.

By Ian Horswill


Posted on September 12, 2019

Astronomers have for the first time found a planet outside the solar system that has properties making it potentially habitable for life.

The discovery by the Hubble Telescope, published in Nature Astronomy, finds the planet, twice the size of Earth, is the only one known to have both water and temperatures that could support life.

Within 10 years new space telescopes, such as the James Webb Space Telescope launched in 2021 and the European Space Agency‘s ARIEL mission in 2028, might be able to determine whether the atmosphere of the planet, known as K2-18b, contains gases that could be produced by living organisms.

The discovery is the first successful atmospheric detection for an exoplanet orbiting in its star’s ‘habitable zone’, at a distance where water can exist in liquid form.

The lead scientist, Prof Giovanna Tinetti, of University College London (UCL), called the discovery “mind blowing”.

“This is the first time that we have detected water on a planet in the habitable zone around a star where the temperature is potentially compatible with the presence of life,” she said.

University College London astronomer Dr Angelos Tsiaras, a coauthor, said at a press conference: “This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it — making this planet the best candidate for habitability that we know right now.”

“This study contributes to our understanding of habitable worlds beyond our Solar System and marks a new era in exoplanet research, crucial to ultimately place the Earth, our only home, into the greater picture of the Cosmos,” he added.

“K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?”

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Astronomer Jonti Horner of the University of Southern Queensland told ABC News that the discovery was the first step towards finding smaller Earth-like planets capable of supporting life.

“The fact we can now make observations that allow us to work out what’s in the atmosphere of a planet twice the Earth’s radius, orbiting a star that is just over a quadrillion kilometres away, is just amazing.”

K2-18b is 111 light-years – about 650 million million miles – from Earth, which is too far to send a space probe.

The only option is to wait for the next generation of space telescopes to be launched in the 2020s and to look for gasses in the planet’s atmosphere that could only be produced by living organisms, said UCL’s Dr Ingo Waldmann.

“This is one of the biggest questions in science and we have always wondered if we are alone in the Universe,” Dr Waldmann added. “Within the next 10 years, we will know whether there are chemicals that are due to life in those atmospheres.”