Sometime this year, the night sky will get a brand new 'star' that will be visible with the naked eye, even in the city. The celestial light show will be the result of an explosive interaction between two neighboring stars that occurs every 80 years.
Located in the Northern Crown constellation, T Coronae Borealis (T CrB) is a pretty average looking star, most of the time. With a brightness of about magnitude +10, it’s right on the limits of what you could see with a pair of binoculars, and even if you do go looking there’s not much to see.
At least, that’s the case for about 79 out of 80 years. But on that 80th year, the star suddenly brightens drastically up to around magnitude +2, which puts it on par with the north star Polaris. That makes it one of the brightest stars in the night sky, easily visible with the naked eye even when washed out by city lights. This once-in-a-lifetime outburst last occurred in 1946, and before that 1866.
And lucky for stargazers, T CrB seems to be about two years ahead of schedule, with astronomers predicting it will flare up again between March and September 2024. It’ll appear as a bright 'new' star for a few days with the naked eye, and a little over a week with binoculars, before it settles down again for another few decades. Astronomers noticed last year that T CrB had started to dim, which data from 1945 showed preceded the last brightening event.
So what causes this predictable, periodic cycle? T CrB isn’t just one star but a binary system consisting of a white dwarf and a red giant locked in a close orbit. The red giant sheds gas at a constant rate and the white dwarf slurps it up, eventually collecting and compressing enough hydrogen to trigger a thermonuclear explosion called a nova. The white dwarf gets hotter, bigger and brighter, which is what we see from Earth as a brief brightening, before it settles back down and starts the 80-year cycle over again.
So keep watching the skies for this once-in-a-lifetime astronomical event, and we’ll keep you posted when the fireworks begin.
Sources: Northeastern University, NASA
