Thursday 19 April 2012

A stellar 'pas de quatre'

We continue our exploration of the Lyra constellation by looking at a very interesting star, Epsilon Lyrae. The constellation Lyra is not hard to find - just look northeast this time of the year and look for the brightest star. That bright star, Vega, is at the top of Lyra. On most nights, Epsilon Lyra would probably appear as a fairly ordinary star near to it (it's just to the left of Vega in the picture below). 


 But on crystal clear nights with no moonlight, your naked eye might well be able to see that  Epsilon Lyrae is actually two stars, very close together. Zoom in near Vega in the picture above and this is what you'll see: 


Train a telescope on that double star and the two components are clearly visible:




It appears to be a binary star system - the northern star is called e1 and the southern one is called e2. They both lie around 162 light years from Earth and orbit each other. However, that is not the end of this star system's surprises. View each of these stars at higher magnifications and you'll see that they both each consist of two stars orbiting each other themselves - making it four stars altogether.   For this reason, Epsilon Lyrae is often called The Double Double.


However, you'd really need a pretty good telescope to 'split' each of these binaries (i.e. to see the four separate star components) because they are very close together. Being able to view the components of each of these binaries is in fact a common benchmark for the resolving power of moderately large telescopes - and my tiny scope unfortunately doesn't quite make the mark if you actually want them through the eyepiece!


Undaunted, with a little bit of image stacking, wavelet adjustments and bumping up the contrast on the video image above, I managed to get the image below, where you can actually see that each of those stars above actually consist of two points of light (especially clear with the pair on the left of the image below):
So we've got two star systems orbiting each other, each of which consists of two stars orbiting each other, and all of them physically connected by gravity and orbiting slowly about their common center of gravity in a cosmic dance. A stellar pas de quatre, in fact.