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An artist’s impression of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system.
An artist’s impression of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system. Photograph: ESO/M. Kornmesser/PA
An artist’s impression of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system. Photograph: ESO/M. Kornmesser/PA

Proxima b will be our prime laboratory in the search for extraterrestrial life

This article is more than 7 years old
Science editor

The discovery of a rocky planet in the habitable zone around our sun’s nearest star is just the beginning of decades of intense research and exploration

Has life gained a foothold on a planet that orbits our nearest star? The question, a variation on one of the greatest mysteries humans have pondered, is now front and centre in astronomers’ minds. The short answer, of course, is nobody knows. But over the coming months, years and decades, scientists will throw every instrument and clever technique they have at Proxima b, an Earth-sized planet warmed by a small, cool star in Centaurus, to find out.

The newfound world has the compelling label of lurking in the “habitable zone”. But planets in this Goldilocks region of space where the heat from their host star makes them neither too hot nor too cold to sustain liquid water, are not necessarily habitable or inhabited. Proxima b may have no flowing water, a prerequisite for life as we know it. On Earth, life flourished with help from an atmosphere and a magnetic field, the latter of which shields us from the worst of space radiation. No one knows if Proxima b has either of these.

And so begins the effort to learn more. Ignas Snellen, a professor of astronomy at the Leiden Observatory calls Proxima b the most important planet found beyond the solar system since the first, 51 Pegasi b, was spotted by Didier Queloz and Michel Mayor in 1995. “This is the discovery of the year and possibly of the decade,” Snellen says. Not only does it mean an Earth-sized planet orbits our nearest star, it implies that other such worlds are common. “It will be our prime laboratory for the search for extraterrestrial life for the decades ahead. We have no idea whether life could exist on this planet, but the circumstances are likely to be much more favourable than on Mars,” he says.

Proxima b - Earth’s new neighbour

The most immediate task is to check whether Proxima b crosses the face of its star as viewed from Earth. Since Proxima Centauri is comparatively small and dim, and thus far less dazzling than sun-like stars, such a transit would allow the Hubble Space Telescope to look for the telltale dip in starlight that the planet’s atmosphere would produce. But the chances are more than 95% that Proxima b orbits in an unhelpful plane.

Without a transit, hopes of finding and studying the planet’s atmosphere fall to future instruments. Hubble’s successor, the James Webb Space Telescope, which is due to launch in 2018, may be the first to peer at Proxima b’s atmosphere. Next in line could be the European Extremely Large Telescope being readied for action in 2024. The goal then will be to spot telltale imbalances in the chemical composition of the atmosphere which are are the calling cards of life.

“People will use Proxima b as a test case. It’s a gift,” says Queloz. “The search for life is not a dream, it’s a serious research topic. There is nothing about magic about life. It is just chemistry and in a way it must happen. Whether it survives and develops is another question,but I really do expect it to be everywhere. Life should not be so special.”

In the language of astronomers, Proxima b is nearby. But 4.2 light years away is 40 trillion kilometres. At the speed of Voyager 1, the only human-made object in the space between the stars, a spacecraft would take 80,000 years to reach Proxima Centauri. With new technology, that could potentially be halved.

This year, the Silicon Valley philanthropist Yuri Milner announced $100m for research into a 20 year journey to Earth’s nearest stars. In reality, such a mission will take billions. But Proxima b gives the project clear focus.

“The importance of this system is as an inspiration,” says Chris Lintott, presenter of The Sky at Night and a professor of astrophysics at Oxford University. “There’s much work to be done to find out what this planet is really like, but the existence of a potentially habitable world just next door should inspire us to explore beyond our solar system. There are existing plans for small, fast-moving probes that could reach Proxima in a couple of decades, and I think just having a target to aim for will inspire more. Now we know it’s there, surely we have to go?”

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