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7 Big Questions About the New Planet Next Door

It’s a discovery for the history books. With its location in our nearest star system and its potential to host life, Proxima b is the most exciting exoplanet found so far. You probably have questions, and we have answers.

Are there aliens on Proxima b?
At the moment, no one can tell. Proxima b is probably similar to Earth in some ways, in mass and temperature, for example, which ups the chance of finding life there. But it is also very different: unlike Earth, one side of the planet is probably in permanent daylight, the other in perpetual darkness. Life could evolve in these conditions, but it’s hard to say, given that we only know of one other example – our own. In any case, if life does exist on Proxima b, it’s more likely to be microbes than little green men.

How can we know for sure?

The number one priority is determining whether Proxima b has an atmosphere. If we can spot its atmosphere and study its chemical composition, that could tell us whether life is present. Signs of oxygen and methane, which break down quickly, would be strong indicators of something living as it would imply the atmosphere is getting a regular supply of these gases. Other gases, such as chlorofluorocarbons, could point to intelligent aliens that have polluted their planet, like us, while ethane could reveal a world that has gone extinct.

Will it take long to find out?
Unfortunately, yes. Unless we get lucky, and Proxima b happens to pass right in front of its star as seen from Earth, we won’t have telescopes powerful enough to see its atmosphere for at least 10 years.

Can we go visit instead?
A crewed mission is basically impossible with current technology, but even sending a robotic probe will be challenging. Proxima Centauri is 4.25 light years away, or around 40 trillion kilometres. That means a journey at light speed, the fastest possible and at the moment well beyond our capabilities, would take this many years. By comparison, the New Horizons spacecraft spent the better part of a decade travelling 5 billion kilometres to reach Pluto last year. A similar mission to Proxima b would last millennia.

Can’t we build something faster?
Early efforts are already under way. A project called Breakthrough Starshot aims to send tiny probes to the Alpha Centauri system, of which Proxima Centauri is a member, using lasers to reach one-fifth of light speed. This would cut the journey time to 20 years. But the launch of such probes is decades away, if indeed they ever get off the ground – the project will need multiple billions of dollars to succeed.

What about sending a message?
That we can do. Astronomers have already used giant radio telescopes to beam messages to other star systems, though some argue we should keep quiet in case we attract the attention of hostile aliens. If we do decide to send a message, it will take 4.25 years to reach Proxima b, and any reply would take the same amount of time to travel back, so it would be almost a decade until we heard anything.

Are there other planets like Proxima b?

Definitely. GJ 667Cc, discovered in 2012 by some of the same team that found Proxima b, is also thought to be rocky and potentially habitable, as are many other planets. Data from NASA’s Kepler space telescope, which has discovered thousands of planets, suggests that around 40 per cent of stars like ours or Proxima Centauri should host similar worlds, meaning there could be 40 billion in the Milky Way galaxy. Extending that out, there could be 100 billion billion in the universe. But Proxima b will always be special, as it’s the closest an Earth could ever be to our own.

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