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Astronomers expect a “new star” to appear in the night sky between now and September in a celestial event that has been in the works for years, according to NASA.
“It is a once-in-a-lifetime event that will create many new astronomers and provide young people with a cosmic event that 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. “It will fuel the next generation of scientists.”
The expected brightening event, known as a nova, will occur in the constellation Corona Borealis or Northern Crown of the Milky Way, which is located between the constellations Boötes and Hercules.
While a supernova is the explosive death of a massive star, a nova refers to the sudden, brief explosion of a collapsed star known as a white dwarf. The dwarf star remains intact and releases material in a repeating cycle that can last thousands of years.
“There are a few recurring novae with very short cycles, but typically we don’t see a repeat eruption very often in a lifetime, and rarely one that is so relatively close to our own system,” Hounsell said. “It’s incredibly exciting to have this front row seat.”
T Coronae Borealis, also known as the ‘Blaze Star’, is a binary system in the Corona Borealis that includes a dead white dwarf star and an aging red giant star. Red giants form when stars use up their supply of hydrogen for nuclear fusion and begin to die. In about 5 to 6 billion years, our sun will become a red giant, swelling and expanding while releasing layers of material and likely vaporizing the solar system’s innermost planets, although Earth’s fate remains unclear, according to NASA.
About every 80 years, T Coronae Borealis experiences an explosive event.
The stars in the orbiting pair are so close together that a violent interaction is possible. The red giant becomes increasingly unstable over time as it warms, shedding its outer layers, which end up as matter on the white dwarf star.
The exchange of matter causes the white dwarf’s atmosphere to gradually warm until it experiences a “runaway thermonuclear reaction,” resulting in a nova, as seen in the animation below, the space agency said.
Keep an eye on the changing skies
In the fall of 1217, a nova was released from T Coronae Borealis when a man named Burchard, abbot of Ursberg, Germany, noticed that he had observed “a faint star shining with great light for a time,” according to NASA. It was the first recorded sighting of the Blaze Star.
T Coronae Borealis last experienced an explosive outburst in 1946, and astronomers are once again keeping a close eye on the galaxy.
“Most novae happen unexpectedly, without warning,” William J. Cooke, head of the NASA Meteoroid Environments Office, said in an email. “However, T Coronae Borealis is one of ten recurring novas in the Milky Way. We know from the last outburst in 1946 that the star will dim for a little over a year before rapidly increasing in brightness. T Coronae Borealis started dimming in March last year, so some researchers expect it to go nova between now and September. But the uncertainty about when this will happen will last several months – it can’t get any better than that with what we know now.”
The star system, located 3,000 light-years from Earth and generally too dim to see with the naked eye, is expected to reach a brightness level comparable to that of Polaris, or the North Star.
Once the nova’s brightness reaches its peak, it will appear as if a new star has appeared: a star that is visible for a few days without any equipment and a little more than a week with binoculars before dimming and for another approximately disappears from view for 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 Crown is a horseshoe-shaped curve of stars west of the constellation Hercules, visible preferably on clear nights,” according to a press release shared by NASA. “It can be identified by locating the two brightest stars in the Northern Hemisphere – Arcturus and Vega – and following a straight line from one to the other, which will lead skywatchers to Hercules and the Corona Borealis.”
Observations around the world
The event promises to be exciting for amateur astronomers, said Dr. Elizabeth Hays, head of the Astroarticle 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. “With the help of social media and email, they immediately send out warnings and the flag goes down. With T CrB we are counting on that global community interaction again.”
Astronomers will observe the nova using a series of telescopes on the ground and in space, and data from citizen scientists can help astronomers piece together what happens before the eruption, Hounsell said.
Normally, nova events are so far away and faint that it’s difficult to identify the full image of the eruption, but “this one will be very close, with a lot of eyes on it,” Hays said.
“Studying returning novae like T Coronae Borealis helps us understand the mass transfer between stars in these systems and provides insight into the thermonuclear runaway that takes place on the white dwarf’s surface when the star goes nova,” says Cooke.
Cooke recalled that the last nova he witnessed – Nova Cygni in 1975 – had a similar brightness to what is expected from T Coronae Borealis. Nova Cygni is not expected to experience another explosion.
“I was a teenage astronomy nerd about to go to college and was outside on the night of August 29,” Cooke said. “When I looked at the sky, I saw that the constellation Cygnus was confused; There was a star that wasn’t supposed to be there. After getting some comments from friends who thought I was crazy, I had them take a look and we realized we were looking at a nova! It was a very memorable experience and solidified my choice of astronomy as a career. I always joked that a star had to explode to make me suffer from my physics studies.
While it’s possible that T Coronae Borealis won’t explode in September, astronomers plan to keep an eye on it just to be sure.
“Recurring novae are unpredictable and unruly,” says Dr. Koji Mukai, astrophysics researcher at NASA Goddard, said in a statement. “If you think there can’t possibly be a reason for them to follow a certain pattern, then they do – and as soon as you start relying on them to repeat the same pattern, they deviate from it completely. We will see how T CrB behaves.”
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