Alpha Centauri is a solar system but it is nothing like ours!

First of all, Alpha Centauri is a solar system in itself not the name of a planet or a star.

It is a triple star system.. which is the major difference to our only star, the Sun, system.

The system itself is made up of 2 stars, Alpha Centauri A (about 10% larger than the Sun) and Alpha Centauri B (about 10% smaller than the Sun) that orbit around a common center of gravity in an eccentric orbit that takes them from 35.6 AU, about the distance from Sun to Pluto to only 11.2 AU, the distance from Sun to Saturn. This orbit takes almost 80 years to complete.

The 3rd star, Alpha Centauri C, it is also known as Proxima Centauri and it is the closest star to our solar system. It orbits rather loosely and it is currently at around 0.21 light years (or about 13,000 AU) to the other two stars and it takes around 550,000 years for it to complete an orbit. Proxima is a small red dwarf, its mass is about 12% of our Sun’s.

For the time being only one planet was confirmed for this system, Proxima Centauri b, which seems to be located in the smaller star’s habitable zone and it is slightly larger than the Earth. However, since Proxima is very active as a star, it can be that the atmosphere of the planet was blown away after the 5–6 billion years since the solar system was born.

It can be that it has a much more powerful magnetic field which protected the atmosphere. If you would stay on the planet you would have a pretty cool view, also during the day, of the other two larger stars.

If, by any chance, Alpha Centauri B has a planet in its habitable zone, it would be even cooler as once every 80 years two suns could be visible during the day. But we are not aware of any existing..

Here’s a view of how a sunset might look on Proxima Centauri b.

An additional planet candidate, Proxima Centauri c was annouced last year (2019), but it wasn’t confirmed just yet. Proxima c is estimated to be a super-Earth, a planet 6 times more massive than Earth, and it completes one orbit around Proxima Centauri every 5.2 Earth years.

It was detected by the radial velocity method, meaning that we didn’t see it transit the parent star. As you can deduce by the long orbital period, it would orbit farther out, at approximately 1.5 AU and the equilibrium temperature, because of the really small size of Proxima, should be at a temperature around minus 390 degrees Fahrenheit (minus 234 degrees Celsius or about 40K).

But equilibrium temperature and the real effective temperature are two different things and atmosphere as well as other factors can up that temperature significantly but this planet should have about the same temperature as Uranus or Neptune.