Brace for Impact: Is the 'Blaze Star' T Corona Borealis on the Verge of a Nova Explosion?

Saturday, March 29, 2025 | Chimniii Desk

Exciting new predictions regarding the so-called "Blaze Star," T Corona Borealis, indicate it could be poised to go nova on March 27, November 10, or June 25, 2026. Yet, some astronomers express skepticism about these forecasts, which are derived from patterns observed in the system's orbital dynamics. As Léa Planquart, a researcher at the Institut d'Astronomie et d’Astrophysique at the Université Libre de Bruxelles in Belgium, noted, "T Corona Borealis [T CrB] is a fascinating object that has captivated both amateur and professional astronomers for over a century."

T CrB is a unique symbiotic binary system, where a white dwarf star is drawing material from a nearby red giant. A white dwarf is a dense remnant of a sun-like star, collapsing its mass into a space approximately the size of Earth. In contrast, a red giant represents a later phase in a star's evolution, during which it expands as it exhausts its hydrogen fuel. The expanded atmosphere of the red giant becomes vulnerable to the stronger gravitational pull of the smaller, denser white dwarf.

Material collected from the red giant forms an accretion disk around the white dwarf, eventually leading to a thermonuclear explosion when enough mass accumulates. This cataclysmic event does not destroy the white dwarf but generates a brilliant nova that can be observed from thousands of light-years away—hence the term "nova," which translates to "new star" in Latin.

Typically, T CrB shines at a faint magnitude of +10, making it only visible through moderate telescopes or large binoculars. However, during a nova event, it brightens to naked-eye visibility, momentarily appearing as a "new star" in the night sky. T CrB is particularly unique, being one of just 11 known "recurrent" novas, which exhibit multiple nova events at intervals of less than 100 years. The last recorded novae occurred on February 9, 1946, and May 12, 1866. Additionally, it is believed that T CrB experienced nova activity around Christmas in 1787, and perhaps even observed again in the autumn of 1217.

In the lead-up to the 1946 nova event, T CrB showed signs of brightness in 1938 before dimming. Similar phenomena were noted recently, as the star brightened by 0.7 magnitudes in 2015 before dimming again in 2023. This pattern has sparked renewed anticipation among astronomers for another nova outburst.

Jean Schneider from the Paris Observatory has observed what he perceives as a correlation between the timing of past nova events in T CrB. The red giant and the white dwarf orbit each other with a period of approximately 227.5687 days, and Schneider theorizes that each nova corresponds to a precise whole number of these orbits. He suggests that the positions of these stars may be responsible for triggering nova explosions.

However, since their orbits are circular, it raises questions regarding specific positions affecting the system. Therefore, Schneider posits that a third body may exist in the T CrB system on a wider elliptical orbit, coming close to the white dwarf approximately every 79 to 80 years. This additional body could enhance the flow of material onto the white dwarf, potentially fostering conditions for a nova event.

To date, this hypothetical third object remains undetected. Schneider indicated that it could be located using methods like astrometry, radial velocity measurements, direct imaging, transits, or microlensing. He even speculates that it may have been detected previously but simply not recognized. A notable increase in brightness of 0.5 magnitudes occurred in the T CrB system on April 21, 2016, which Schneider links to the possible movement of this undetected third body into a closer position.

Nonetheless, some astronomers remain unconvinced. Léa Planquart, who published a study earlier this year examining mass transfer in T CrB, notes that their decade-long radial velocity observations have not yet provided evidence of a third star. "While Jean Schneider suggests a companion in an eccentric orbit," she stated, "our monitoring does not detect this additional orbital motion." While it is feasible that a low-mass object akin to a large exoplanet could exist, definitive proof is lacking.

Skepticism also arises from Jeremy Shears, the Director of the British Astronomical Association's Variable Star Section, who cautions that the predictions merit close monitoring. "Most astronomers harbor doubts about this forecast," he noted, adding, "the best course of action is to keep vigilant each clear night."

Should the predictions not stem from the influence of a third object and if Schneider's observed patterns in past nova dates are mere coincidences, what lies ahead for T CrB?

Planquart’s findings illuminate the situation. The brightness increase from 2015 to 2023 suggests that the accretion disk around the white dwarf reached a critical size, becoming hotter and brighter. This phenomenon, which Planquart describes as the "vampirization effect," facilitates a super-active phase of mass transfer to the white dwarf. However, in 2023, the disk cooled once more, leading to a subsequent dimming, though material continues to flow into the white dwarf at a slower pace.

Questions remain about what causes this state change in the accretion disk that leads to periods of heightened activity and the processes occurring on the surface of the white dwarf leading up to the anticipated nova.

Although Schneider’s specific predictions may not materialize, the recurring pattern of heightened activity followed by quiescence indicates a nova could be imminent. "We may anticipate an explosion within the next few months, perhaps next year," stated Planquart.

When that spectacular event unfolds, stargazers can expect another bright display; T CrB reached a magnitude of +2 during its last nova, becoming easily viewable to the naked eye, akin to the stars in the Big Dipper. Shears believes it could shine just as brightly this time around.

Currently, T CrB resides within the constellation Corona Borealis, the Northern Crown, which is visible across the Northern Hemisphere and as far south as South Africa and Australia, albeit at low elevations. "Currently at tenth magnitude, T CrB can only be observed with large binoculars," explained Shears. "However, as it increases in brightness, it will become observable with regular binoculars and eventually to the naked eye."

The brightening, once it begins, is expected to happen swiftly. "The rise could occur within mere hours—though the exact timeframe remains uncertain as we’ve never documented such a rapid increase before," noted Shears. This excitement fuels hopes that plenty of observers will be on hand to witness the star's awakening process.

As anticipation builds, many astronomers will be on the lookout for this rare nova, aiming to better understand the dynamics occurring on the surface of the white dwarf during this extraordinary thermonuclear explosion. "When it eventually detonates, it is set to be one of the most extensively monitored celestial events, capturing the attention of telescopes worldwide," added Planquart.

Looking forward, the future of T CrB holds even more explosive potential. The white dwarf in this system has a mass 1.37 times that of our sun, pushing it close to the Chandrasekhar limit of 1.44 solar masses. This threshold represents the point at which a thermonuclear reaction could ultimately lead to the destruction of the white dwarf in a Type Ia supernova. As the white dwarf continually siphons mass from its partner red giant star, it propels its own eventual doom.