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What on earth is T Coronae Borealis playing at? We’ve been on alert for it to explode since April, when we confidently expected it to go boom some time before September. But we are still waiting.
The star is a recurrent nova. This means it actually consists of two stars: a red giant and a white dwarf. The white dwarf is a dense stellar core about the size of the Earth, whose gravity is stripping gas from the red giant. The gas accumulates on the white dwarf’s surface before detonating in a thermonuclear explosion, causing the star to temporarily brighten. This does not destroy the white dwarf, which then returns to normal and the cycle repeats.
Historically, T Coronae Borealis blows its stack and reaches naked-eye brightness once every 80 years or so, and it should be blowing any day now. The chart shows the view looking west from London at 20.00 BST on 7 October.
When T Coronae Borealis does finally put on its show, it is expected to reach the same brightness as Alphecca, the brightest star in its constellation. Unfortunately, as the Latin name suggests, it is not easily visible from the southern hemisphere.