A red giant star and a white dwarf orbit each other in this animation of a nova similar to T Coronae Borealis. The red giant is a large sphere in red, orange and white, with the side facing the white dwarf in the lightest shades. The white dwarf is hidden in a bright glow of white and yellow, representing an accretion disk around the star. A stream of material, shown as a diffuse red cloud, flows from the red giant to the white dwarf. When the red giant moves behind the white dwarf, a nova explosion ignites on the white dwarf, creating a ball of ejected nova material, shown in light orange. After the mist of material clears, a small white spot remains, indicating that the white dwarf survived the explosion. Credit: NASA/Goddard Space Flight Center
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A red giant star and a white dwarf orbit each other in this animation of a nova similar to T Coronae Borealis. The red giant is a large sphere in red, orange and white, with the side facing the white dwarf in the lightest shades. The white dwarf is hidden in a bright glow of white and yellow, representing an accretion disk around the star. A stream of material, shown as a diffuse red cloud, flows from the red giant to the white dwarf. When the red giant moves behind the white dwarf, a nova explosion ignites on the white dwarf, creating a ball of ejected nova material, shown in light orange. After the mist of material clears, a small white spot remains, indicating that the white dwarf survived the explosion. Credit: NASA/Goddard Space Flight Center
This summer, both professional and amateur astronomers around the world will be fixated on one tiny constellation deep in the night sky. But it is not the seven stars of Corona Borealis, the ‘Northern Crown’, that have aroused such fascination.
It’s a dark place below them where an impending nova event – so bright it will be visible to the naked eye on Earth – is about to take place.
“It is a once-in-a-lifetime event that will create many new astronomers, giving young people 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. “It will fuel the next generation of scientists.”
T Coronae Borealis, also called the ‘Blaze Star’ and known to astronomers simply as ‘T CrB’, is a binary system nestled in the Northern Crown, about 3,000 light-years from Earth. The system consists of a white dwarf – an Earth-sized remnant of a dead star with a mass comparable to that of our Sun – and an ancient red giant slowly being stripped of hydrogen by the brutal gravity of its hungry neighbor .
The red giant’s hydrogen builds up on the white dwarf’s surface, creating pressure and heat. Ultimately, it causes a thermonuclear explosion large enough to blow away the accumulated material. For T CrB, this event appears to occur on average every 80 years.
Don’t confuse a nova with a supernova, a final, gigantic explosion that destroys some dying stars, Hounsell said. In a nova event, the dwarf star remains intact, shooting the collected material into space in a blinding flash. The cycle typically repeats over time, a process that can take tens or hundreds of 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.”
A conceptual image of how to find Hercules and the ‘Northern Crown’ in the night sky, created using planetarium software. During the summer months, look up after sunset to find Hercules, then scan between Vega and Arcturus, where the distinct pattern of Corona Borealis can be identified. Credit: NASA
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A conceptual image of how to find Hercules and the ‘Northern Crown’ in the night sky, created using planetarium software. During the summer months, look up after sunset to find Hercules, then scan between Vega and Arcturus, where the distinct pattern of Corona Borealis can be identified. Credit: NASA
Finding T Coronae Borealis
The first recorded sighting of the T CrB nova was more than 800 years ago, in the fall of 1217, when a man named Burchard, Abbot of Ursberg, Germany, noted his sighting of “a faint star shining for a time with great light” .
The T CrB nova was last seen from Earth in 1946. Its behavior over the past decade is strikingly similar to that observed in a similar time frame leading up to the 1946 eruption. If this pattern continues, some researchers say , the nova event could happen in September 2024.
What should stargazers pay attention to? The Northern Crown is a horseshoe-shaped curve of stars west of the constellation Hercules, visible preferably on clear nights. 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 sky watchers to Hercules and the Corona Borealis.
The eruption will be short-lived. Once the volcano erupts it will be visible to the naked eye for just under a week, but Hounsell is confident it will be a beautiful sight to see.
A coordinated scientific approach
Dr. Elizabeth Hays, head of the Astroarticle Physics Laboratory at NASA Goddard, agreed. She said part of the fun of preparing to observe the event is seeing the enthusiasm among amateur stargazers, whose passion for extreme space phenomena has helped maintain a long and mutually rewarding partnership with NASA .
“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 alerts and the flag goes down. We are counting on that global community interaction with T CrB again.”
Hays is the project scientist for NASA’s Fermi Gammaray Space Telescope, which has been making gamma-ray observations from low Earth orbit since 2008. Fermi is poised to observe T CrB when the nova outburst is detected, along with other space missions including NASA’s James Webb Space Telescope, Neil Gehrels Swift Observatory, IXPE (Imaging X-ray Polarimetry Explorer), NuSTAR (Nuclear Spectroscopic Telescope Array) , NICER (Neutron star Interior Composition Explorer) and the European Space Agency’s INTEGRAL (Extreme Universe Surveyor).
Numerous ground-based radio telescopes and optical imaging sensors, including the Very Large Array of the National Radio Astronomy Observatory in New Mexico, will also participate. Together, the various telescopes and instruments will record data about the visible and non-visible light spectrum.
“We will observe the nova event at its peak and during its decay, as the visible energy of the eruption fades,” Hounsell said. “But it is just as important to obtain data during the early rise to the eruption – so the data collected by those enthusiastic citizen scientists now searching for the nova will dramatically contribute to our findings.”
For astrophysics researchers, this promises a rare opportunity to shed new light on the structure and dynamics of recurring stellar explosions like this one.
“Normally, nova events are so faint and distant that it is difficult to clearly identify where the eruptive energy is concentrated,” Hays said. “This will be very close, with many eyes on it, studying the different wavelengths and hopefully giving us data to unlock the structure and the specific processes involved. We can’t wait to get the full picture of what’s going on.”
Some of those eyes will be very new. The last time T CrB erupted in 1946, gamma-ray cameras did not yet exist, and the polarization capability of IXPE – which identifies the organization and alignment of electromagnetic waves to determine the structure and internal processes of high-energy phenomena – is also a completely new technique. tool in X-ray astronomy. Combining their data could provide unprecedented insight into the life cycles of binary systems and the waning but powerful stellar processes that fuel them.
Is there any chance that September will come and go without the expected nova outburst of T CrB? Experts agree there are no guarantees, but hope remains.
“Recurring novae are unpredictable and unruly,” says Dr. Koji Mukai, a fellow astrophysics researcher at NASA Goddard.
‘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’ll see how T CrB behaves.”