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Wait Continues for Eruption of T Coronae Borealis

“When it explodes, it will be one of the most extensively observed objects,” says astrophysicist Léa Planquart.

Artist’s impression of T Coronae Borealis. The white dwarf star on the left is pulling material—mostly hydrogen—away from the red giant on the right.

An artist’s impression of T Coronae Borealis, which is composed of two stars. The white dwarf star on the left is “vampirizing” the red giant on the right. When the white dwarf accumulates too much material, it explodes. (Based on Planquart et al 2025.)

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A Once-in-80-Years Event

As we reported last year, astronomers and hobby stargazers are on standby for the eruption of T Coronae Borealis, also known as T CrB or the Blaze Star.

T Coronae Borealis is normally invisible to the naked eye. But every 80 years or so, it erupts in a thermonuclear explosion and—for a few days only—becomes one of the 50 brightest stars in our night sky.

How Can We See T Coronae Borealis?

When it explodes, the Blaze Star will be visible for a few days to skywatchers around the world. It will be about the same brightness as Polaris, the North Star.

T CrB will appear next to Corona Borealis, a crown-shaped constellation from which it takes its name.

You can find and track T Coronae Borealis from your town or city using our Night Sky Map.

timeanddate.com’s Night Sky Map shows the position of T Coronae Borealis, as seen from Sydney at 05:00 local time on March 31, 2025.
timeanddate.com’s Night Sky Map shows the position of T Coronae Borealis, as seen from Sydney at 05:00 local time on March 31, 2025.

You can use our Night Sky Map to follow the position of T Coronae Borealis as it moves across the sky.

©timeanddate.com

T CrB Is Actually Two Stars

Léa Planquart, an astrophysicist at the Université libre de Bruxelles in Belgium.

Léa Planquart’s work is based on more than a decade of observation of T CrB with the Mercator Telescope in the Canary Islands. Together with her colleagues, she continues to observe the star regularly at the Mercator Telescope, hoping to catch the explosion at its rise and study its aftermath.

What’s going on with T CrB, and why is the date of the eruption difficult to predict?

Léa Planquart, an astrophysicist at the Université libre de Bruxelles in Belgium, has been studying the mechanisms and behavior of T CrB.

“T Coronae Borealis is a unique object that has been fascinating amateur and professional astronomers for more than a century,” she tells timeanddate.com.

“This astronomical object is composed of two stars. One star is a cool red giant, about a hundred times larger than our Sun. The other is a white dwarf, of the size of Earth for a mass similar to the Sun.”

A Vampire Star?

Over time, the white dwarf pulls material—mostly hydrogen—away from the red giant.

“The white dwarf is vampirizing its red giant companion,” says Planquart.

“More precisely, their close presence deforms the red giant surface, which now has the shape of a blood drop pointing toward the white dwarf. The white dwarf extracts the matter from the tip of the giant’s surface to form a ring of matter around it, called an accretion disc.

“A nova explosion occurs when the white dwarf has accumulated too much material. The pressure becomes so high it induces a thermonuclear explosion that blows the accumulated material away.”

She adds that a nova should not be confused with a supernova, which is a much more violent astrophysical phenomenon.

The Trigger Point

How close are we to the Blaze Star’s next explosion?

“We realized that in recent years, from 2015 to 2023, the accretion disc around the white dwarf has reached its maximum extension and become hotter and more luminous, leading to increased system brightness,” Planquart explains.

“The increased disc temperature has actually enhanced the vampirization effect, amplifying the matter transfer through the white dwarf.

“This increased brightness—which we refer to as the superactive phase—is reminiscent of what happened several years before the last eruption in 1946.

“So it is likely that this enhanced activity is needed to trigger the nova explosion as it allows the material to accumulate faster.”

Uncertainty Remains

But there is still much for astronomers to learn about T CrB.

According to Planquart, “Since mid-2023, the system has been back to a more quiescent phase, meaning that the accretion disc has cooled down. We do not know how long this quiet phase will last.

Given what we’ve learned from previous explosions, “we could hope to see the explosion in the coming months . . . or next year . . .”

Anticipation Is Sky High

What is clear is that the astronomy community is excited.

“T Coronae Borealis is an exceptional laboratory for studying a nova explosion,” enthuses Planquart.

“When it explodes, it will be one of the most extensively observed objects, targeted by telescopes around the globe.”