Nature could hardly have been kinder to us. The discovery of a potentially habitable planet on our astronomical doorstep is nothing short of astronomers’ wildest dreams coming true.
In a world where discoveries seem to be coming thick and fast (think water on Mars, gravitational waves, Higgs boson) it is vitally important that we now focus our efforts on learning all we can about this tantalising world because of its potential to tell us something about life elsewhere in the universe.
Proxima Centauri b is about 1.3 times the mass of the Earth. Its year lasts just 11.2 days, and it lies in the so-called ‘habitable zone’ of its parent star, the dim red dwarf known as Proxima Centauri.
Humans have speculated about life elsewhere in the universe for millennia. This planet gives us a real chance of pursuing answers because although similar worlds have been discovered before, none have been this close to us.
The parent star, Proxima Centauri, is the closest star to the Sun at just 4.24 light years away. This means that the planet could not be more ideally placed for follow-up investigations – maybe even a visit.
As luck would have it, in April this year, a group called Breakthrough Initiatives, whose board consists of Stephen Hawking and Mark Zuckerberg, announced Breakthrough Starshot.
Travelling to the stars is incredibly difficult because of the distances involved. The aim of Breakthrough Starshot is to invest $100 million to demonstrate that a spacecraft could be built to reach Proxima Centauri’s distance in a journey time of ‘only’ 20 years.
Now that we know of the planet at Proxima Centauri, it becomes Breakthrough Starshot’s most obvious target. Were we to go – and were there to be life – there is so much this newly discovered world could potentially tell us about ourselves.
We do not know how life began on Earth. We do not know if life has to be based on DNA. We do not know whether life can only exist in a narrow range of conditions or is resilient to a wide range of extreme environments. If – and it is still a big if – there is even the simplest microbial life on Proxima Centauri b, it would be a real chance to look for these answers.
The next few years are going to see an intense period of activity using ground-based telescopes to learn more about Proxima Centauri b.
So far astronomers have only inferred its presence because of the wobble its gravity induces on its parent star. If they can isolate its light, they can search for clues to the composition of its atmosphere.
This is no easy task. It is akin to seeing a fire-fly crawl around the rim of a searchlight that is pointing right at you. But it is possible and the rewards are extraordinary because the planet’s atmosphere could betray whether it is inhabited or not.
On Earth, oxygen built up because cyanobacteria evolved metabolisms based on photosynthesis. This releases oxygen as a waste gas and throws the atmosphere out of ‘chemical equilibrium’.
Measuring the gases in the atmosphere of Proxima Centauri b could therefore show us whether it too was out of chemical equilibrium or not. If it were, the chances are that it is indeed a living world, and that would surely spur the desire for a space mission to go there despite the high technological hurdles.
The parent star itself needs more study too. We know that it occasionally undergoes huge outbursts of X-rays, which could damage any life that has gained a foothold on the world.
Nevertheless, the discovery of Proxima Centauri b is a clarion call to the world’s astronomers, physicists, chemists and biologists. It is a natural laboratory ripe for exploration and the work is far bigger than any one country can achieve alone.
Whether we find life there or not, in exploring this nearby world, we could help bring our own closer together.
Stuart Clark is the author of The Search for Earth’s Twin (Quercus), and co-host of the podcast The Stuniverse (Bingo Productions).
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