The past year has been littered with can’t-miss space phenomena: the solar eclipse and Aurora Borealis, for example. It isn’t rare to witness some cosmic events. Others, like Halley’s Comet or the Great Conjunction, are so rare that they only come along once in a lifetime. That’s why it’s such big news that T Coronae Borealis, also known as the Blaze Star or T CrB, is headed toward a cosmic explosion that’ll shine brighter than the North Star. It’s an event we may only ever see happen once – and if you blink, you just might miss it.
In February 2016, astronomers began to share the news that T CrB had entered a “phase of unprecedented high activity.” Eight years later, experts are predicting that solar activity could result in a nova event big enough to be viewable from Earth with the naked eye.
In a nova event, a white dwarf star pulls in solar material from a nearby red giant. When the heat and pressure get too high, the result is a thermonuclear explosion. That makes the white dwarf appear brighter in the sky, but it doesn’t disintegrate, and once the explosion dissipates, the star goes back to its original brightness. That massive eruption is a nova.
The nova can be seen with the naked eye for upward of a week after it happens. For that period, it’ll seem like a new star has appeared in the sky. According to NASA, the explosion could happen anytime, day or night, between now and September, although scientists say it may take longer.
What will the Blaze Star nova look like?
Those fortunate enough to be looking at the night sky when the show starts may be disappointed. It won’t look as explosive as it actually is. According to Dr. Elizabeth Hayes, project scientist for the Fermi Gamma-ray Space Telescope at NASA’s Goddard Space Flight Center, someone looking at the sky when the event occurs won’t see anything right away.
“If they keep watching for the next 24 hours, they will see a faint star appear and gradually brighten,” Hayes told CNET. “Of course, someone on Earth will have their view interrupted as the Earth rotates.”
Normally, the red dwarf of T CrB has a stellar magnitude of 10 — the lower the number the brighter. When the nova explosion occurs, the star system will increase to magnitude 2, or nearly as bright as Polaris, the North Star.
“The best time to look by eye will be about one day into the eruption,” Hayes said. “But the nova will be visible by eye for a few days.”
This NASA video shows what it looks like.
The last nova from T CrB happened 78 years ago
The cosmic light show is courtesy of T Coronae Borealis, also known as the Blaze Star or T CrB. It’s a binary star system comprising a white dwarf and an ancient red giant about 3,000 light years away from Earth in the Northern Crown of the Milky Way. It’s part of the Corona Borealis constellation that makes a distinctive “C” shape in the sky, primarily during the summer months.
The white dwarf, which is the dead remnant of a star, is about the size of Earth but has the same mass as the sun. Meanwhile, the aging red giant is a dying star that’s shedding material out into space. The white dwarf’s massive gravitational pull is hauling in the ejected material from the red giant. Once the white dwarf has accumulated enough material, the heat increases so much that it causes a runaway thermonuclear reaction. That explosion is called a nova.
The prior nova from this star system occurred in 1946. It’s a cycle that’s been going on since it was first discovered more than 800 years ago.
“It’s a once-in-a-lifetime event that will create a lot of new astronomers out there, giving young people a cosmic event they can observe for themselves, ask their own questions, and collect their own data,” said Rebekah Hounsell, an assistant research scientist at NASA’s Goddard Space Flight Center. “It’ll fuel the next generation of scientists.”
Where is Corona Borealis?
You likely aren’t as familiar with Corona Borealis as you are with constellations that are easier to spot, like the Big Dipper. It’s difficult to find in the night sky unless it’s clear. Light pollution from major cities can also make it more difficult to find.
NASA says the easiest way to find Corona Borealis is to find Vega and Arcturus, the two brightest stars in the Northern Hemisphere. (Skygazing apps for your phone might help with this.) From there, you can essentially draw an imaginary line between the two. Corona Borealis is almost right in the middle. You can use the graphic below to see what we mean.
The nova will happen in the Corona Borealis constellation near the Hercules constellation and right between Vega and Arcturus.
Alternatively, you can also seek out the Hercules constellation and Corona Borealis will be right next to it. Remember that you can’t see the star in question until the nova pops, so if you look up in the sky before it happens, the spot where the nova will occur won’t be visible.
When will the T CrB nova occur?
Nobody knows for sure. Astronomers and scientists only know that the nova is due to erupt at any time. Most of them agree that the nova should take place around September, although it could take longer.
Since the nova could occur at any moment, NASA is relying on citizen astronomers and space enthusiasts to call it out when the nova happens.
“Using social media and email, (observers will) send out instant alerts,” said Elizabeth Hays, chief of the Astroparticle Physics Lab at NASA Goddard. “We’re counting on that global community interaction again with T CrB.”
Early detection can also help NASA collect more data about the event to better understand its mechanics.
“We’ll observe the nova event at its peak and through its decline, as the visible energy of the outburst fades,” Hounsell said. “But it’s equally critical to obtain data during the early rise to eruption — so the data collected by those avid citizen scientists on the lookout now for the nova will contribute dramatically to our findings.”
Do I need a telescope to see the nova?
No. NASA says the nova will be visible to the naked eye on a clear night. It’ll also be pretty bright, so it should be fairly noticeable. As always, folks with telescopes and binoculars will have a better view.
People with high-powered telescopes will see the changes more definitively.
“A telescope that measures the optical spectrum would see something very different from the red giant spectrum,” said Hayes. They’ll see “nova eruptions emit spectral lines at specific wavelengths. These tell us about the elements in the explosion and how fast the blastwave travels away from the white dwarf.”
The nova won’t look like an explosion like you see in Michael Bay movies. It’ll simply look like another star in the sky that wasn’t there previously.
What’s the difference between a nova and a supernova?
Most people have heard of the term “supernova.” It’s the last dying gasp of a star as it goes dark. That last dying gasp also happens to be the largest explosion ever witnessed by humans, as the star violently ejects material into space. Scientists believe that supernovas are responsible for elements heavier than iron in the universe. Weirdly enough, even the iron in your blood can be traced back to supernovas or similar cosmic explosions.
A nova, on the other hand, requires two stars. One star is always a white dwarf, while the other is usually a red giant.
There are other types of novas as well. Hypernovas are supernovas that achieve a certain size and brightness. Usually, they’re about 10 or more times brighter than a standard supernova. Another type, an extremely rare kilonova, occurs when two neutron stars collide, releasing an incredible gravitational wave along with electromagnetic radiation.
