We live on a planet that we call Earth which, along with a number of other worlds, orbits a star which we call the Sun. In theory a planetary system is a natural bi-product of star formation. Thus, every star should be accompanied by a retinue of planets. However, until recently we did not have the technology to detect them.
This has all changed with discoveries made by giant space telescopes. We can currently confirm the existence of almost 6,000 planets around other stars. Many more await confirmation. Think about it. Our galaxy contains approximately 150,000 million stars. If only one in a thousand of these stars have a planet similar to the Earth in size, mass and climate, Earth-like worlds must number more than a hundred million. And, that is just in our galaxy.
Where do we look to find these other Earths? The answer is…right on our doorstep! When you have a clear, dark evening sky go out and look for the ‘Southern Cross’. It is, on a September evening, in the south-west. You can identify the Cross by the two bright ‘Pointer Stars’ that follow it around the sky.
The brighter of the two ‘Pointer Stars’ is Alpha Centauri. It is, at a distance of 4.367 light-years, the nearest star beyond the Solar System. I have always had a fascination for this star. Not just because it is the closest star, but because it has the potential to support another Earth-like world. There are however, some major differences between the Solar System and the Alpha Centauri System.
Seen through a telescope Alpha Centauri is a double star. It is a binary system of two suns that orbit around each other in a period of 79.8 years. The distance between the two stars varies. At their closest the separation is equivalent to that between our Sun and Saturn.
The brighter of the two stars has a mass 110% that of our Sun and is 52% brighter. The companion star has a mass of 97% of our Sun and a luminosity of 50%.
It has been recently confirmed that a planet similar to Saturn orbits around the brighter star. Other planets appear to be present around both stars and work continues to identify their properties. How would you like to live on a world with two suns?
Richard Hall
Stonehenge Aotearoa
Photo Credit: NASA and G. Bacon (STScI) – https://hubblesite.org/contents/media/images/2003/19/1370-Image.html