So which is the closest star to Earth, besides the Sun. I always thought it was Alpha Centauri. Recently I saw a chart that claimed Proxima Centauri was the closest.
Did they find a new star? Is Alpha Centauri a Binary, consisting of Proxima and Dista Centauri? What gives? Which is the closest?
Proxima Centauri is the closest star beyond our sun. Alpha Centauri, the three-star system, includes Proxima Centari and is the closest star system. Alpha Centauri: The Closest Star System.
Cool! Thanks!!
Wait a few million short years and Proxima Centauri will no longer be the closest star. It will be on the other side of the binary system, which it orbits.
Last I’d heard, there was actually some doubt that Proxima was gravitationally bound to the Alpha Cen system… It may be a parabolic or hyperbolic orbit, and just happens at the present time to be relatively close to the other two stars of Alpha Cen.
THere is some doubt in cetain quarters, but it isn’t the view of the majority. Given the know measures of radial velocity and distance (from each other) Proxima appears to be in the grip of Alpha Centari, but barely. This is similar to the situation with the four outermost moons of Jupiter, it wouldn’t take much to free them. And since scientists are looking for planets around Proxima Centauri and could detect a “0.0015 arcsec amplitude perturbation” it seems to me that they know it’s properties quite well. But it wouldn’t take much of an error in the radial velocity to put Proxima Centauri in a parabolic orbit.
I don’t know, but I’m inclined to say it orbits.
I’ve always thought Tau Ceti was our closest neighbour at 3.4 lights, whereas I thought Alpha Cen was about 4 lights.
Alas, I’ve nothing to hand to be able to check 
4.3 light years sounds right for the distance to Alpha Centauri.
Like JonF said, it’s thought to be a 3-star system where Proxima Centauri is currently the closest to our sun. (thus the name Proxima)
What Chronos said was interesting…I’ll keep an eye out for more info on this.
Tau Ceti is visual magnitude 3.49
It’s 12 light years away. Sirius is closer, as well as twenty five other stars.
We did this one in February –
http://boards.straightdope.com/sdmb/showthread.php?threadid=12693
(in fact, I was the OP)
Tau Ceti is significant in that it’s the closest single G-type star to the Sun (G-type being the Sun’s type). Alpha Centauri B is also G-type, but it’s in a binary (or trinary) system. The significance of this, is it’s considered unlikely for life to evolve around a binary star (but then, what do we know?), and we know for a fact that life can evolve around a single G-type star, so Tau Ceti is considered a pretty good prospect (as stars go) for finding extraterrestrial life nearby.
I can see the discussion now, at Spacewatch:
Bottke (breathless): Bob! We found an object headed straight for the Earth!
McMillan (rubs hands in anticipation of government funding): Great! How many nukes are we going to need? Are we going to have enough time?
Bottke (chagrined): Yeah, we have some time. It’s Proxima Centauri. Nukes, well, I dunno…
Life can exist (on planets orbiting binary stars)! I know it! Luke Skywalker was born on Tatooine, which has two suns!
Hey, I never said it was impossible, I said it was unlikely. Notice that Tatooine is the only inhabited planet in the Star Wars galaxy with two suns? We can’t rule out life in the Alpha Cen system, but we can even less rule it out around Tau Ceti.