Alpha Centauri is one of my favourite stars and it just got even more interesting. Astronomers from the European Southern Observatory have found a planet orbiting around it.
These days finding another exoplanet, that is a planet that orbits a distant star, isn’t so unusual. We know of over 800 exoplanets and the Kepler spacecraft has spied 2,000 more that are waiting confirmation.
But this one is special because of its star. Here’s why…
Alpha Centauri is lovely and bright, the third brightest star in the night sky, and it is prominent in our southern sky. It is the brighter star of the Two Pointers, which lead us to the Southern Cross.
Alpha Centauri (yellow star on the far left) and Beta Centauri (blue star to the right of Alpha Centauri) point towards the Southern Cross.
Image: Akira Fujii
Source: Akira Fujii
Alpha Centauri is also great to look at through a telescope. What appears as a single bright star in the night sky, becomes two stars when seen through even a modest telescope. Both of the Sun-like stars – Alpha Centauri A and Alpha Centauri B – are quite similar so it looks like you’re seeing double. (A fair distance away there’s a third star too, Alpha Centauri C or Proxima Centauri, a faint red dwarf star).
At just over four light years away (or roughly 40 million million km) Alpha Centauri is the closest star to our Sun. If ever we manage to develop the capability for space travel, this is sure to be the star system we set our sights on.
And now it has a planet! The planet is orbiting Alpha Centauri B and it was hard to find, taking over four years of observations. Many follow up investigations will now begin so as to be absolutely certain.
Artistic impression of the planet around Alpha Centauri B.
Source: ESO/L. Calcada/Nick Risinger
The new found planet has a mass similar to Earth, but takes only 3.2 days to orbit the star. It’s a scorched world, with temperatures soaring over 2000°C.
But finding one planet in this star system is really encouraging and there just might be others. If a planet was found at a more reasonable distance from this Sun-like star, it would be very interesting as far as life is concerned.
Any night sky talk I’ve ever given always includes Alpha Centauri. It’s exciting after all these years to learn something new about it.