Astronomers expect a “new star” to appear in the night sky anytime between now and September in a celestial event that has been years in the making, according to NASA.
“It’s a once-in-a-lifetime event that will create a lot of young astronomers out there, giving young people a cosmic event they can observe for themselves, ask their own questions and collect their own data,” said Dr . Rebekah. Hounsell, an assistant research scientist specializing in nova events at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “This will feed the next generation of scientists.”
The expected lighting event, known as a nova, will occur in the Milky Way’s Corona Borealis constellation, or the Northern Crown constellation, which lies between the constellations Boötes and Hercules.
While a supernova is the explosive death of a massive star, a nova refers to the sudden and brief outburst from a collapsed star known as a white dwarf. The dwarf star remains intact, releasing material in a repeating cycle that can occur for thousands of years.
“There are some recurring novae with very short cycles, but typically, we don’t often see a recurring outburst in a human lifetime, and rarely one so relatively close to our system,” Hounsell said. “It’s incredibly exciting to have this front row seat.”
T Coronae Borealis, also known as “The Flaming Star”, is a binary system in Corona Borealis that includes a dead white dwarf star and an aging red giant star. Red giants form when stars have exhausted their supply of hydrogen for nuclear fusion and begin to die. In about 5 billion or 6 billion years, our sun will become a red giant, swelling and expanding as it sheds layers of material and will likely vaporize the inner planets of the solar system, though Earth’s fate remains unclear, according to NASA.
Every 80 years or so, T Coronae Borealis experiences an explosive event.
The stars in the orbital pair are close enough to each other that they interact violently. The red giant becomes increasingly unstable over time as it heats up, shedding its outer layers that land as matter on the white dwarf star.
The exchange of matter causes the white dwarf’s atmosphere to gradually heat up until it experiences a “runaway thermonuclear reaction,” resulting in a nova as seen in the animation below, according to the space agency.
Keeping an eye on the changing sky
A nova was being emitted from T Coronae Borealis in the fall of 1217 when a man named Burchard, abbot of Ursberg, Germany, noted his observation of “a faint star which for a time shone with great light,” according to NASA. It was the first recorded observation of the Blaze Star.
T Coronae Borealis last experienced an explosive outburst in 1946, and astronomers are keeping a watchful eye on the star system once again.
“Most novae happen suddenly, without warning,” said William J. Cooke, head of NASA’s Meteoroid Environment Office, in an email. “However, T Coronae Borealis is one of 10 recurring novae in the galaxy. We know from the last explosion in 1946 that the star will dim for just over a year before rapidly increasing in brightness. T Coronae Borealis it began to fade in March last year, so some researchers expect it to go nova between now and September, but the uncertainty of when that will happen is a few months – it can’t do much better than that with what we know now .
The star system, located 3,000 light-years from Earth and usually too dark to see with the naked eye, is expected to reach a brightness level similar to that of Polaris, or the North Star.
Once the nova reaches its peak brightness, it will be as if a new star has appeared—one that is visible for a few days without any equipment and a little more than a week with binoculars before it fades and disappears from view for about another 80 years.
The nova will appear in a small arc between the constellations Boötes and Hercules and will be visible from the northern hemisphere.
“The Northern Corona is a horseshoe-shaped curve of stars to the west of the constellation Hercules, ideally seen on clear nights,” according to an announcement shared by NASA. “It can be identified by finding the two brightest stars in the northern hemisphere – Arcturus and Vega – and tracing a straight line from one to the other, which will lead sky watchers to Hercules and Corona Borealis.”
Observations around the world
The event promises to be an exciting event for amateur astronomers, said Dr. Elizabeth Hays, head of the Astroparticle Physics Laboratory at NASA Goddard.
“Citizen scientists and space enthusiasts are always looking for those strong, bright signals that identify nova events and other phenomena,” Hays said. “Using social media and email, they’ll send instant alerts and the flag goes up. We’re counting on that global community interaction with T CrB again.”
Astronomers will observe the nova using a variety of ground- and space-based telescopes, and data from citizen scientists can help astronomers piece together what happens before the explosion as well, Hounsell said.
Typically, nova events are so distant and faint that it’s hard to identify the full picture of the explosion, but “this is going to be really close, with a lot of eyes on it,” Hays said.
“Studying recurrent novae like T Coronae Borealis helps us understand mass transfer between stars in these systems and provides insight into the thermonuclear escape that occurs at the surface of a white dwarf when the star goes nova,” Cooke said.
Cooke recalled that the last nova he saw – Nova Cygni in 1975 – had a brightness similar to that expected from T Coronae Borealis. Nova Cygni is not expected to experience another outburst again.
“I was an astronomical teenager about to start college and I was out on the night of August 29,” Cooke said. “Glancing up at the sky, I noticed that the constellation Cygnus was messed up; it was a star that shouldn’t be there. After enduring a few comments from friends who thought I was crazy, I asked them to look and realized that we were looking a nova was a very memorable experience and reinforced my choice of astronomy as a career.
While it’s possible that T Coronae Borealis won’t erupt until September, astronomers plan to monitor it just in case.
“Recurrent novae are unpredictable and opposite,” said Dr. Koji Mukai, an astrophysics researcher at NASA Goddard, in a statement. “Just when you think there can’t be a reason why they follow a certain certain pattern, they do—and as soon as you start relying on them repeating the same pattern, they completely deviate from it. We’ll see how T CrB behaves.”