Proxima b | Vol. 3 / No. 43.4

A home away from home? | Image: ESO / M. Kornmesser, CC BY 4.0 International

Yesterday, scientists from the European Southern Observatory announced that the rumoured discovery of an Earth-sized planet at our closest stellar neighbour, Proxima Centauri, was in fact not just a rumour. The team, led by Guillem Anglada-Escude at the Queen Mary University of London, have presented what appear to people much smarter than me to be very solid data, so this planet is unlikely to be some kind of statistical blip.

What do we know?

Its parent star is Proxima Centauri. It’s a red dwarf of just under 1/8 the mass of the Sun, and a diameter of just under 1/7 that of the sun. You can’t see it with the naked eye because it’s so dim. It’s the closest extrasolar star, at 4.25 light-years away.

Its name is “Proxima Centauri b” or just “Proxima b” to its friends. Accoring to convention, planets are named using their parent star and lower-case letters, starting with b.

It’s in its parent star’s habitable zone. The so-called “goldilocks zone” where it’s possible for water to be liquid on the surface. Its surface temperature sans-greenhouse-gases would be -40°C, which sounds pretty bad until you realize ours would be -15°C.

It orbits at just 5% the distance from its parent star that we do from the Sun. We’re 146 million km from the sun, it’s only 7.3 million km from Proxima Centauri — but Proxima Centauri is so dim it’s possible that isn’t a problem, even though from the planet’s surface the star would appear three times as big as the Sun does from here.

Its year is only 11.2 of our days long. That sounds pretty insane, but its star is so small that that means its only going at one or two metres per second. We’re hurtling around the Sun at thirty kilometres per second.

Its mass is at least 1.3 times the Earth’s. We have a 90% probability that it’s less than 2.3 times the mass of Earth. So while it’s not certainly a rocky planet, if it isn’t it’s probably something exotic. Franck Marchis suggests the possibility of a “baby Neptune” which sounds pretty cool (though not as cool as a life-covered Earth cousin, of course). That doesn’t mean you’d weight 1.3-2.3 times as much on its surface — that number depends on its density and how far you are from its center.

It’s not a shoe-in for habitability, but it’s not ruled out, either. Red Dwarfs have a habit of giving off flares and other radiation that could do a number on an unprotected atmosphere. On the other hand, it could have a kick-butt magnetic field that protects it. We just don’t know.

What don’t we know?

Pretty much anything else. We don’t even know the angle it’s orbiting at or the precise shape of its orbit, which is why we aren’t sure of its mass or size. We only know it’s there because it’s causing Proxima Centauri to “wobble” a tiny bit. But the good news is that the next generation of telescopes should be able to see it even better, and maybe eventually we’ll get an actual image of it. How cool would that be?

If you want more info on it, there are a ton of sites out there with more detail. Check out Franck Marchis’s post over at The Planetary Society, Phil Plait’s post over at Slate’s Bad Astronomy blog, and the ESO’s press release to get the full scoop.

And, of course, you can watch this handy-dandy video made by the ESO to announce their discovery:

I can’t tell you how excited I am by this news. It’s in our backyard! But it’ll still take us lifetimes to get there without the invention of some new amazing form of propulsion, and even if we got up to relativistic speeds, we’d still have issues with running into killer stardust. That said, it gives us something to look at with those next generation telescopes, and may even give us something to strive for in the decades to come. The future’s looking up.


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Richard Ford Burley is a human, writer, and doctoral candidate at Boston College, as well as an editor at Ledger, the first academic journal devoted to Bitcoin and other cryptocurrencies. In his spare time he writes about science, skepticism, feminism, and futurism here at This Week In Tomorrow.