Topline
Scientists have announced that a dim star in a constellation easily visible after dark from the Northern Hemisphere is finally on the verge of exploding. The binary star system, called T Corona Borealis (TCrB), dramatically brightens approximately every 80 years and was last observed doing so in 1946, making it a once-in-a-lifetime event. It could become visible to the naked eye next week.
Key Facts
According to recent observations and predictive models, the long-anticipated “nova” (new star) is thought to be heading for an eruption on Thursday, March 27, 2025, after which it's predicted to become visible to the naked eye for a few nights. It should become about as bright as the North Star, the 48th brightest star in the night sky.
T Corona Borealis is a binary star system around 3,000 light-years away in the constellation Corona Borealis, the "Northern Crown." It consists of a white dwarf star (a star that’s exhausted its fuel and is cooling down) and a red giant star (a star that's cooling and expanding as it ages, expelling material as it does.
Over time, the white dwarf accumulates material spilling from the red giant star until it finally triggers a thermonuclear explosion. This explosion causes a sudden and dramatic increase in brightness, allowing the star, usually too dim to see, to become visible to the naked eye from Earth.
There are records of TCrB exploding in 1787 and 1866 as well as in 1946, making it a predictable event seen by different generations of astronomers. That’s also the case with Halley’s comet, which comes close to Earth every 76 years.
T Corona Borealis: Imminent Explosion
It’s known from previously observed events that T CrB dips in brightness considerably before it explodes and brightens. The American Association of Variable Star Observers reported that it had dipped in brightness in March/April 2023, predicting that the star would go nova around April 2024. That didn't happen, but astronomers have closely monitored T CrB ever since.
“Since last September, detailed observations of the star have revealed variations that suggest the imminent arrival of this long-awaited explosion,” said Franck Marchis, SETI Institute astronomer and Co-founder of smart telescope maker Unistellar, which intends to begin an observation program, in an email. “However, as the study is still theoretical, its conclusions remain uncertain.”
How To Find T Corona Borealis In The Night Sky
The constellation Corona Borealis — a curve of seven stars — rises in the east about three hours after sunset, as seen from the Northern Hemisphere, and will be easy to see an hour after that. It’s between the constellations Boötes and Hercules.
Find bright star Arcturus, due east, by tracing the stars in the handle of the Big Dipper in a curve towards the horizon. Now find the bright star Vega, rising in the northeast. Corona Borealis is roughly between the two. A good way for astronomers to find it is to look halfway between Arcturus and the “Great Globular Cluster” known as M13 in the constellation Hercules.
Further Reading