Alpha Centauri has a planet!

Exoplanetologists have found a planet orbiting Alpha Centauri B! This is a pretty huge discovery, since Alpha Centauri is the closest star system to our own, and even if this planet is far too warm to harbour life, this discovery shows there might well be other, more friendly planets in the same system.

Alpha Centauri consists of three stars orbiting each other: there's Alpha Centauri A, a yellow dwarf like our Sun, Alpha Centauri B, an orange dwarf about half as bright as our Sun, and Proxima Centauri, a tiny red dwarf that emits very little light. Alpha Centauri A and B orbit each other once every 71 years at about 3 billion kilometres, approximately 20 times the radius of Earth's orbit, or about the radius of Uranus' orbit. Proxima Cenaturi orbits very distantly from the other two, at 2 trillion kilometres, orbiting once in many thousands of years. The newly discovered planet, Alpha Centauri Bb, orbits very closely around Alpha Centauri B, only 6 million kilometres from it. It's nearly ten times closer to its sun than Mercury, so its temperatures are so high there's a good chance the planet's surface is molten.

Alpha Centauri Bb is only a little bit heavier than Earth, and probably about the same size too. If you were there, the skies would look much like they do from Earth, as most stars are far more distant. However, the constellation Cassiopeia (the W shaped one) would have a sixth bright star added to it, continuing the constellation's zigzag pattern. This star would of course be our Sun. Alpha Centauri B would look like a gigantic ball of intense light, 300 times brighter than the Sun from Earth, and its light would burn you to a crisp within a second. Alpha Centauri A would be a single point of very bright light that would complete a circle around the sky every 71 years, like a very bright planet. It would be 100 times dimmer than our Sun, yet still 4000 times brighter than our full Moon. Its light would be similarly bright to a street lantern. Proxima Centauri, the final sun of the system, would barely be visible at all; it's so dim and so distant you would only be able to see it on dark nights, and then it would look like just another dim star.

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