Scientists predicted this star would explode. It's bucked expectations.

For centuries, stargazers have watched a new star light up in the sky. Just days later, it vanishes.

Today we call the star system responsible T Coronae Borealis, "T CrB" for short, or the "Blaze Star." It fires up around every 80 years, and NASA noted that astronomers expected to see the star appear around the summer of 2024. It's now 2025. What gives?

This repeating event — occurring 3,000 light-years from Earth — is triggered by two interacting, orbiting stars. An Earth-sized star called a white dwarf (the dense remnants of an exploded sun-like star) is ripping gas away from a nearby red supergiant star. Years pass, and prodigious amounts of gas amass on the white dwarf's surface. Under such extreme heat and pressure, the surface blows in a violent thermonuclear reaction, called a nova.

But a precise deep space prediction is difficult.

"We’re waiting for a 'new' star to briefly make an appearance, but we don’t know exactly when it will occur. The star is pulling material from a companion star, and over decades it collects enough to trigger an eruption," NASA recently explained in a post. "But we don’t know how fast the material is piling up!"

The space agency added that "we have clues that it may erupt soon, but 'soon' could mean today or next year!" (That's "next year" as in 2026.)

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Although scientists had high hopes for a 2024 spectacle, the star's elusive behavior isn't too surprising. We're still learning about these cosmic explosions.

"Recurrent novae are unpredictable and contrarian," Dr. Koji Mukai, a NASA astrophysicist, said in a 2024 statement. "When you think there can’t possibly be a reason they follow a certain set pattern, they do — and as soon as you start to rely on them repeating the same pattern, they deviate from it completely. We’ll see how T CrB behaves."

How to see T Coronae Borealis when it explodes

Although T Coronae Borealis' timing isn't certain, astronomers know for certain where it'll appear in the night sky. NASA explains:

What should stargazers look for? The Northern Crown is a horseshoe-shaped curve of stars west of the Hercules constellation, ideally spotted on clear nights. It can be identified by locating the two brightest stars in the Northern Hemisphere — Arcturus and Vega — and tracking a straight line from one to the other, which will lead skywatchers to Hercules and the Corona Borealis.

(In the summer months, the Northern Crown appears in the sky after sunset, which makes ideal viewing.)

But you'll have to act fast. After erupting and appearing, it'll only be visible with the naked eye for less than a week, similar to how watchers viewed it long ago, during the Middle Ages, if not much earlier.

The location of T Coronae Borealis in the night sky. Credit: NASA

If it behaves as (generally) expected, the exploded star will reappear in another 80 or so years, after prodigious amounts of stellar gas settle onto its surface.

Then, boom.