Astronomers watch for zombie star to rise again

A long-dead star is set to go nova soon, making it visible in the evening sky for a short time. It’s not

About every 80 years, the T Coronae Borealis star system – or T CrB for short – explodes violently, relighting a long dead star.

Earlier this year there were strong indications that T CrB was ready to create this new visible star for a few days. This hasn’t happened yet, but history suggests it’s just a matter of time.

Exact predictions can be tricky when you’re talking about something happening 3,000 light-years away.

Red giant + white dwarf

The T CrB system is actually two stars. More than half the stars we see in the night sky have one or more partners.

It is made up of a red giant, a star in the later stages of its lifespan, bloated to hundreds of times its original size. Our own Sun will be there in about 5 billion years.

The other is a white dwarf, an incredibly dense, Earth-sized remnant of a dead star. Since 1946, that dark, dense white dwarf has been siphoning off stellar material from its red giant partner, like a vampire.

But the dead star can only draw so much of its companion’s life force. Once it reaches critical mass, the surface layers explode in an event called a nova, which makes it visible to the naked eye for a few days.

Records of pervious T CrB nova events go back more than 800 years. A man named Burchard wrote in 1217 of observing “a faint star that for a time shone with great light” from his home in Ursberg, Germany.

Amateur astronomers and professional scientists alike are eagerly awaiting the event.

“Typically, nova events are so faint and far away that it’s hard to clearly identify where the erupting energy is concentrated,” explained Dr. Elizabeth Hays, chief of the Astroparticle Physics Laboratory at NASA Goddard. “This one will be really close, with a lot of eyes on it, studying the various wavelengths and hopefully giving us data to start unlocking the structure and specific processes involved. We can’t wait to get the full picture of what’s going on.”

How and when to find T CrB

T CrB will be visible to the naked eye, but it is unclear when — it could be days, weeks or even months.

Once visible, T CrB, also known as the “blaze star”, will appear between the bright stars Vega and Arcturus in the western sky after sunset. If this happens in the next few weeks, Venus can also help provide a guidepost.

We don’t know exactly when this is going to happen, but it is likely to happen soon.

Nova or supernova?

This will be a nova, not a supernova event.

Unlike supernovas, which destroy the star, novas only eject the accumulated layers of stellar material and can happen again and again. Novas brighten for days at most, while supernovas significantly brighten for up to months.

Recent changes in Betelgeuse, a red supergiant star in the constellation Orion, have fueled speculation that it might go supernova “soon.” A 2023 paper studied the star’s brightening and dimming and concluded that a “supernova explosion is expected in a few tens of years.”