HOW TO SEE A STAR GOING NOVA

on 28 May 2024.

I had better start at the beginning, what does going nova mean? The word comes from Latin and means new. In astronomy it refers to a new star, a star that suddenly appears in the night sky. This happens because a star suddenly increases in brightness from one that is invisible to the naked eye, to one that can be seen.

Stars are graded in brightness, the dimmest that can be seen with perfect eyes on a very clear night are called magnitude 6 and the lower the number the brighter the star. The bright star Vega in the constellation Lyra is magnitude 1 and a full moon is minus 13.
Ok, so now you know what a nova star is, please don't confuse it with a supernova, a very rare event when a certain type of star massively explodes.
The nova star I'm taking about is actually 2 stars very close together, a binary star, in this case a very large red giant and a white dwarf in close orbit around each other, and what happens between them is fascinating.
The white dwarf is a shrunken old star that has used up all its fuel, but still has lots of mass and gravity. Over time its gravity attracts material, mostly hydrogen from the red giant which builds up on the surface. It keeps doing this until there is so much that it gets hot and explodes. As you can imagine a huge layer of gas on even a small star’s surface gives off a huge flash, and the event can last for several days, this is a nova.
The star that will be having this event is called T Coronae Borealis, and it’s about 3000 light years from Earth. Coronae Borealis is an easy to find constellation in our northern sky near Hercules, not far from the star Vega I mentioned earlier.
It’s quite unusual for us to know when a star is likely to do this, but in this case we know that it goes off about every 80 years, and is now due. Assuming it doesn’t happen between me writing and you reading this, it should happen before September, and go to a similar brightness to the pole star, Polaris.
As far as is known, there are less than a dozen systems like this in our galaxy, so this is quite a special event. To see it go out on a clear night and find the constellation, then look carefully at the stars, and make a mental note of where the star T (Theta Coronae Borealis) is. Then look again through binoculars, and you’ll see the star, it’s quite dim. When it goes nova, you’ll see a massive difference, and have witnessed one of the wonders of astronomy. It should stay bright for up to a week, so you can let your imagination loose on what it would look like close up.
Happy observing everyone.

Charles Oates, Vega Baja Astronomy Group.

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