Astronomers Are Watching for a Once-in-a-Lifetime Nova Explosion. When Will We See It?

Astronomers and sky-watching hobbyists alike are waiting to witness a rare event that will light up in the night sky. The blast, called a nova, might be the brightest of its kind that many of us will see in our lifetimes. The last time this nova erupted was in 1946. Now, nearly 80 years later, some astronomers had predicted it would light up again by September this year—but that month has come and gone.

Even though the nova hasn’t happened yet, amateur and professional astronomers are continuing to keep a close watch on the sky. And when the much-anticipated blast does occur, we may still get a front-row seat.

The “Blaze Star,” as it’s been named, or T Coronae Borealis (T CrB), is located in the summer constellation Corona Borealis that can be found almost directly overhead in the evening during July and August. Situated some 3,000 light-years away from Earth, the Blaze Star is a binary system in which a white dwarf, the core remains of a dying star, accumulates material from its neighboring red giant star.

The nova, also referred to as a thermonuclear explosion, occurs when enough material from the red giant builds up in the white dwarf to power a bright outburst. When it erupts, the star system will become much more luminous, appearing like a new star in the sky.

“We hope that it happens any day now,” Rebekah Hounsell, a nova researcher at NASA’s Goddard Space Flight Center, told the Indianapolis Star in early September. But astronomers are careful to say that the blast can’t be exactly predicted. “The timing of when it does happen is an estimate,” she added. “We hope this year, we hope this month.”

Why can we see novae?

We’re able to spot novae when faint stars, in this case the Blaze Star, rise to peak brightness due to an outburst of material, then fade to their pre-eruption level. They can remain at peak brightness anywhere from days to months.

A star’s brightness, or its “magnitude,” is measured on a logarithmic scale. Brighter stars have a lower value, sometimes dipping into the negative numbers, and fainter stars have a higher value, as Paul Barrett, a physicist at George Washington University, explains in an email to Smithsonian magazine. Only about 50 novae happen each year in the Milky Way, and most of them are not bright enough to spot.

T CrB generally sits at a magnitude 10, which is too dim to be seen with the naked eye. But at the peak of its eruption, it could become as bright as magnitude 2, according to NASA. That’s about as bright as Polaris, the North Star, per the Planetary Society. Polaris is one of the brightest stars in the night sky, and it was used for navigation by sailors before more modern inventions.

Around the world, professional and amateur astronomers are closely watching T Coronae Borealis – a binary system ~3,000 light-years from Earth – waiting for an impending nova event so bright it will be visible on Earth with the naked eye.

MORE HERE >> https://t.co/HgONmjpy9B pic.twitter.com/L54ZDFmFWA

— NASA Marshall (@NASA_Marshall) June 6, 2024

The upcoming nova will remain visible to the naked eye for a bit less than a week, NASA predicts.

Supernovae, which are much brighter explosions, are in a class of their own. Novae like T CrB are called cataclysmic variable stars, because their outbursts are not catastrophic—they don’t destroy the white dwarf. Supernovae, meanwhile, occur at the end of a star’s life and result in the formation of either an ultra-dense neutron star or a black hole.

When will the nova occur?

The Blaze Star is a recurrent nova, meaning it has been seen several times throughout history. The recurrence time, in this case, is what makes this nova rare and special. Recurrent novae tend to go hundreds or thousands of years between blasts, but this one had its last eruption in 1946. And before that, it appeared in 1866—showing up around every 80 years.

T CrB might also have been observed in 1217 by German monks and by a British astronomer in 1787, writes Bradley E. Schaefer, an astronomer and astrophysicist at Louisiana State University, for Sky & Telescope.

Despite the nova’s periodic nature, it’s difficult for astronomers to pin down exactly when it will occur. The prediction that T CrB would erupt this summer was based on a drop in brightness observed in March 2023. This behavior is similar to what the star system did before its 1946 outburst, Sarbani Basu, an astronomer at Yale University, tells Smithsonian magazine in an email.

“The system became dimmer for about a year before the last eruption, which is what was seen happening for this system,” she adds. As a result of that behavior, astronomers predicted the outburst would happen this summer.

But making such an estimate isn’t easy. Given its 80-year timeframe, “if the outburst occurred now, it would be about two years early,” Barrett says. “So, we may have a year or more to wait.”

How to get a front-row seat to see T CrB

When the star system finally does go nova, “you’re going to notice a new star in the sky,” Bill Cooke, lead of NASA’s Meteoroid Environment Office, told the New York Times’ Robin George Andrews in March.

A chart or app depicting the night sky could help observers locate the nova, and “it should be easily visible to everyone when at peak brightness, if you know where to look,” Barrett says.

T CrB is also relatively nearby and bright, so when it erupts, it is easily visible to the naked eye. “Novae with the brightness of T CrB only occur a few times per century,” Barrett adds. “That is what makes it so special.”

Astronomers are waiting with anticipation for this rare nova, because it will offer unprecedented opportunities for research. The last time T CrB erupted, there were no X-ray or gamma-ray telescopes in space, reports Space.com’s Sharmila Kuthunur. Now, scientists’ high-tech instruments could gather new data on the blast.

But sky-watchers are paying close attention for another reason, too—Corona Borealis, the constellation where the nova will appear, is going to move behind the sun from the Earth’s perspective as the year goes on, Basu says. So, viewers are facing a limited window to see it.

Still, amateur astronomers and hobbyist organizations are keeping an eye out to catch the eruption when it occurs. NASA is counting on a global community that includes amateur stargazers.

“Citizen scientists and space enthusiasts are always looking for those strong, bright signals that identify nova events and other phenomena,” says Elizabeth Hays, chief of the Astroparticle Physics Laboratory at NASA Goddard, in a statement. “Using social media and email, they’ll send out instant alerts, and the flag goes up.”

Another current program is happening with the American Association of Variable Star Observers (AAVSO), a nonprofit composed of amateur and professional astronomers, where observers from all parts of the world “check T CrB on average once every 12 minutes every hour of every day,” writes Schaefer for Sky & Telescope.

Whether the nova happens today, next week or even next year, with astronomers keeping an eye on the sky, we will all have the best chance possible to witness this spectacular explosion as it makes history.

Alexa Robles-Gil | | READ MORE

Alexa Robles-Gil is a bilingual science journalist based in New York City. Her work has appeared in the Guardian, Undark, Inside Climate News and more.