Alpha Centauri

31 December 2018

How well do you know your neighbours?

Alpha Centauri (Rigil Kentaurus, or just Rigel Kent) is not just a single star. It’s not even a double, it’s probably a triple.

Alpha Centauri A and B appear as two stars very close to each other in a telescope. You have to have a scope with a long focal length to be able to split the two.

When I was a kid, we used to judge how good people’s scopes were by looking at Alpha Centauri to see if the scope could split the binary pair. To do it, the scope needed a lot of light gathering ability, good optics, and a long focal length.

That probably also suggests a lot about what I was like as a kid.

The distance between these two stars is only about 11 times the distance between the Earth and the Sun. The pair dance with each other, taking about 80 years to complete a do-si-do. Any planets nearby would be well cooked.

Their poor neighbour, Alpha Centauri C, is dull red, nearly invisible and also about 0.2 light years away from the others. It’s on the wrong side of an awful lot of railway tracks.

There’s some debate as to whether Alpha Centauri C is even part of the Alpha Centauri "system", as it’s a long way away from the others, and takes about 500 million years to circle the others.

But Alpha Centauri C is the closest star to the Sun. It's known as Proxima Centauri.

It’s got at least one planet, Proxima b, nicely in the star's "habitable zone". If there's water there, it could be found in liquid form.

If that doesn’t make it cool, get this – NASA is doing the early stages for a mission to Proxima b, probably for late this century. It will likely be a fly-by, rather than an orbit, as screeching to a halt consumes too much fuel.

Just think of that. It’ll be something for my grandchildren to see.

Image: NASA