A star that usually hides from view could suddenly pop into sight and rival the North Star.
T. Coronae Borealis, also called T CrB or the Blaze Star, is a recurring nova. NASA says systems like it are extremely rare, with only five known in the Milky Way.
The system undergoes a thermonuclear explosion from the atmosphere of a white dwarf roughly once every 80 years, after the star strips material from a co-orbiting red giant and reaches critical mass. After each eruption, the white dwarf begins feeding on its companion again.
Historical observations spanning eight centuries show T CrB brightens about once every 80 years on average. The last nova light reached Earth in 1946.
Some astronomers had predicted the next brightening could happen as early as February 2024, based on an earlier dip in the system’s light that matched historical data. That did not happen, and the system has remained dim through several failed prediction attempts.
“We know it has to happen,” astrophysicist Elizabeth Hays, project scientist on NASA’s Fermi gamma-ray space telescope, told Space.com in 2024. “We just can’t pin it down to the month.”
A paper by Jean Schneider of the Paris Observatory proposed four possible dates for the brightening, with the last on June 25, 2026, based on a theoretical third body in the T CrB system. The source article said other astronomers were sceptical because modern data has not shown evidence of that third body.
When T CrB erupts, its apparent brightness surges as radiation from the event reaches Earth after travelling for about 3,000 years through space.
Normally, T CrB is far too faint to see without equipment, with an average magnitude of about +10. During a nova, it can brighten to magnitude +2, making it visible to the naked eye and comparable in brightness to Polaris.
The star sits near the semicircle of stars in Corona Borealis, the Northern Crown, between Bootes and Hercules after sunset in early summer.
Before any brightening, observers need 10 x 50 binoculars or a small telescope to spot it. The source article says to first find Epsilon Coronae Borealis, a magnitude 4.28 star and the second star in from the left of the semicircle as seen from the Northern Hemisphere. From there, look about one degree to the lower right, roughly the width of a little finger held at arm’s length, for the patch of sky containing T CrB.
NASA says the nova should remain visible to the naked eye for a little under a week. Binoculars should let observers follow it for longer.
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