Are you lonesome tonight is a favourite song of many of us sung by the singer of all times – Elvis Presley. Surely, however, this song was not devoted to our Sun. For a good reason though.  Our Sun has no reason to suffer of isolation and negligence.  In fact, Sun is not alone in our galaxy – so-called Milky Way – but it is surrounded by other 200 billion stars.  Its most neigbouring star Proxima Centauri is just in its doorstep. Other neighbours such as Sirius lie also very close indeed.  So, why our Sun should be feeling lonesome?

You may, of course, ask yourselves. All right, all right; but where is anyway this doorstep of our Sun? I can’t see it? And where is this Sirius?

Well, actually there is a good chance that you have already seen Sirius several times, even though you may not have realised it.  This is because Sirius is the brightest star in the night sky.  You can’t miss it.  Nevertheless, during winter times a simple way to find Sirius is to look at the virtual extension of the Orion belt (three bright adjacent stars).

From Orion belt to Sirius

Now, concerning the doorstep of our Solar System this is defined by the outer limit of the so-called Oort Cloud and it is about 0.6 pc (parsec) or in other words 2 ly (light years) from the Sun itself.  Just have in mind that at the stellar level the whole solar system dominates a space called Heliosphere the edge of which forms a magnetic bubble. This bubble, in turn, lies within a bigger sphere known as the Oort Cloud the outer bounds of which consist of cosmic dust. This sphere has  a radius of 0.6 pc and as a center our Sun.

So, at a distance of 0.7 pc outside the Oort Cloud lies Proxima Centauri.  A little bit further, namely at a distance of 2 pc outside the Oort Cloud lies Sirius.  So, one of the reasons why Sirius shines so bright in the night sky is that it is very close to us. Of course, another reason is also its intrinsic luminosity which in turn is due also to its magnitude: it is twice as big as our Sun.