NASA, global astronomers await rare nova explosion

This summer, professional and amateur astronomers around the world will be fixated on one small constellation deep in the night sky. But it is not the seven stars of the Corona Borealis, the “northern crown” that have caused such fascination.

It’s the dark spot in between where an impending nova event is poised to occur – so bright that it will be visible on Earth with the naked eye.

“It’s a once-in-a-lifetime event that will create a lot of new astronomers and give young people a cosmic event to observe for themselves, ask their own questions and collect their own data,” said Dr. Rebekah Hounsell, associate scientist specializing in nova events at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It will drive the next generation of scientists.”

T Coronae Borealis, nicknamed the “Blaze Star” and known simply as “T CrB” to astronomers, is a binary system nestled in the Northern Corona about 3,000 light-years from Earth. The system consists of a white dwarf—the Earth-sized remnant of a dead star with a mass comparable to that of our Sun—and an old red giant that is slowly being stripped of hydrogen by the relentless gravity of its hungry neighbor.

Hydrogen from the red giant accumulates on the surface of the white dwarf, causing pressure and heat to build up. Eventually, it will set off a thermonuclear explosion large enough to detonate the accumulated material. UT CrB appears to repeat this event every 80 years on average.

Don’t confuse a nova with a supernova, the last titanic explosion that destroys some dying stars, Hounsell said. In the event of a nova, the dwarf star remains intact and the accreted material is hurtled into space in a blinding flash. The cycle usually repeats itself 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 we don’t usually see repeated flares very often in human lifetimes, and rarely ones that are relatively close to our own system,” Hounsell said. “It’s incredibly exciting to have this front row seat.”

Discovery of T Coronae Borealis

The first recorded sighting of a nova T CrB was more than 800 years ago, in the fall of 1217, when a man named Burchard, an abbot of Ursberg in Germany, recorded his sighting of “a faint star which for a time shone with a great light.”

The T CrB nova was last seen from Earth in 1946. Its behavior over the past decade bears a striking resemblance to that seen over a similar time frame leading up to the 1946 eruption. If this pattern continues, some scientists say the nova event would could happen by September 2024.

What should stargazers look for? The northern corona is a horseshoe-shaped curve of stars west of the constellation Hercules, ideally visible on clear nights. It can be identified by locating the two brightest stars in the northern hemisphere—Arcturus and Vega—and tracing a straight line from one to the other that takes sky watchers to Hercules and Corona Borealis.

The explosion will be short. Once it explodes, it will be visible to the naked eye for just under a week – but Hounsell is confident it will be quite a sight.

A coordinated scientific approach

Dr. Elizabeth Hays, head of the Astroparticle 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 beneficial partnership with NASA.

“Citizen scientists and space enthusiasts are always looking for those strong, clear signals that identify nova events and other phenomena,” Hays said. “With social media and email, they send instant alerts and the flag goes up. We look forward to this global community interaction with T CrB again.”

Hays is a project scientist for NASA’s Fermi Gamma-ray Space Telescope, which has been making gamma-ray observations from low Earth orbit since 2008. Fermi is ready to observe T CrB when a nova eruption 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 INTEGRAL (Extreme Universe Surveyor) of the European Space Agency.

A number of ground-based radio telescopes and optical imaging facilities will also participate, including the National Radio Astronomy Observatory’s Very Large Array in New Mexico. Together, the various telescopes and instruments will capture data across the spectrum of visible and invisible light.

“We will observe the nova at its peak and during its decline as the visible energy of the explosion fades,” Hounsell said. “But it’s just as important to get the data during the early rise of the eruption – so the data collected by those passionate citizen scientists now looking for the nova will add dramatically 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.

“Typically, nova events are so faint and distant that it’s hard to clearly identify where the energy of the eruption is concentrated,” Hays said. “This one is going to be really close, there’s going to be a lot of eyes on it, it’s going to study different wavelengths and hopefully it’s going to give us the data to start unlocking the structure and the specific processes involved. We can’t wait to get the full picture of it , what’s happening.” “

Some of those eyes will be very new. In the last eruption of T CrB in 1946, gamma-ray imagers did not 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 quite new. a tool in X-ray astronomy. Combining their data could offer unprecedented insight into the life cycles of binary systems and the fading but powerful stellar processes that drive them.

Is there a chance that September will come and go without the expected nova explosion from T CrB? Experts agree there are no guarantees — but hope remains.

“Recurring novae are unpredictable and contradictory,” said Dr. Koji Mukai, an astrophysicist fellow at NASA Goddard.

“Just when you think there can be no reason why they follow a certain set pattern, they do – and once you start relying on them repeating the same pattern, they completely deviate from it. We’ll see how T CrB behaves.”