Corona Borealis, the northern crown, could be about to add another jewel – at least for a while. A star system there has been flaring up every 80 years. The last outburst was in 1946, so it’s due for the next one.

T Corona Borealis is actually a binary – two stars locked in a mutual orbit. One of them is a white dwarf – the “corpse” of a star that was once like the Sun. The other is a red giant – a star that’s puffed up as it nears the end of its own life.

The white dwarf pulls hydrogen off the surface of its bloated companion. The gas forms a spinning disk around the white dwarf. Gas at the inner edge of the disk spirals onto the white dwarf. The white dwarf’s gravity is quite strong, so the infalling gas is squeezed into a thin layer and heated to tens of millions of degrees. That eventually triggers a runaway nuclear explosion – like a giant hydrogen bomb. The outburst is known as a nova – a Latin word that means “new.”

When the “bomb” goes off, the system shines tens of thousands of times brighter than average. That makes it visible to the eye alone, even though it’s 3,000 light-years away. So keep an eye out for this “new” jewel in the northern crown.

Corona Borealis is high in the southwest at nightfall. It’s an upside-down semicircle of stars, with the brightest star at its middle. T Corona is close to the top left end of the semicircle.

We’ll talk about another bright nova tomorrow.

Script by Damond Benningfield