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Astronomers have released new predictions regarding the next outburst of T Corona Borealis, a recurrent nova also known as the “blaze star.” These forecasts suggest the star may experience a nova explosion around March 27, November 10, or June 25, 2026. However, some astronomers remain skeptical of these timelines, which are based on a perceived pattern in the binary system’s orbital configuration.
T Corona Borealis: A Century-Long Enigma
“T Corona Borealis [T CrB] is a unique celestial object that has captivated both amateur and professional astronomers for over a century,” stated Léa Planquart of the Institut d’Astronomie et d’Astrophysique at the Université Libre de Bruxelles in Belgium, in a discussion with Space.com.
Symbiotic Binary System
T CrB is classified as a symbiotic binary, a “vampire system” where a white dwarf is actively drawing material from a red giant star. A white dwarf is the incredibly dense remnant of a sun-like star‘s core, compressing stellar mass into a volume comparable to the size of Earth. Conversely, a red giant represents a later evolutionary phase for a star similar to our sun, occurring as it exhausts its hydrogen fuel and begins to expand. This expanded atmosphere becomes an accessible source of matter for the significantly smaller, yet denser, white dwarf’s gravitational pull.
The Nova Phenomenon
The matter extracted from the red giant forms a swirling accretion disk around the white dwarf. This material gradually accumulates on the white dwarf’s surface. When a sufficient amount has amassed, it triggers a thermonuclear explosion. This event, known as a nova – Latin for “new star” – does not destroy the white dwarf but produces a burst of light visible across vast cosmic distances of thousands of light-years.
Recurrent Nova: A Repeating Celestial Spectacle
Typically, T CrB exists at a faint magnitude of around +10, requiring mid-sized telescopes or strong binoculars for observation. However, during a nova event, its brightness dramatically increases, becoming visible to the unaided eye as a “new star” in the night sky.
Adding to its distinctiveness, T CrB is one of only 11 known recurrent novas. These systems exhibit repeated nova outbursts at intervals of less than a century. Previous nova explosions from T CrB were recorded on February 9, 1946, and May 12, 1866. Historical records also suggest a nova around Christmas of 1787, with an estimated earlier event possibly observed in the autumn of 1217.
Pre-Nova Brightening and Dimming
Leading up to the 1946 nova, T CrB experienced a slight increase in brightness in 1938, followed by a dimming phase just before the explosion. A similar pattern has been observed recently in T CrB, with a 0.7 magnitude brightening in 2015 preceding a dimming in 2023, raising expectations among astronomers for another impending nova.
The Third Body Hypothesis
Jean Schneider of Paris Observatory has identified a potential pattern in the timing of T CrB’s nova events. He notes that the red giant and white dwarf complete an orbit around each other every 227.5687 days. Schneider proposes that each nova outburst occurs after a period equivalent to a whole number of these orbital cycles, suggesting a link between the orbital configuration and nova triggers.
However, the near-circular orbits of the binary pair complicate this theory, as no specific orbital position should inherently initiate an explosion. To address this, Schneider suggests the presence of a third, undetected object in the T CrB system, following a wider, elliptical orbit. He theorizes that approximately every 79–80 years, this third object approaches the white dwarf, augmenting the flow of matter onto the white dwarf from both the red giant and this additional source, thereby enhancing the conditions conducive to a nova.
Search for the Unseen Companion
As of yet, this hypothesized third object remains undetected. Schneider suggests to Space.com that, “it could be detected by astrometry, radial velocity, direct imaging, a transit or microlensing.”
He also speculates whether the object might have already been observed but not recognized as a separate body. He points to an event on April 21, 2016, when the T CrB system exhibited a sudden 0.5 magnitude increase in visual brightness.
“I have the following, subjective assessment, which is that before then, the third body was outside the pixel corresponding to the visual measurements,” he explained, suggesting the third object moved into close enough proximity to be captured within the same pixel as the primary binary components, adding its light to their combined luminosity.
Skepticism and Alternative Explanations
Despite these intriguing ideas, other astronomers are not yet convinced. Léa Planquart, who studies T CrB and other recurrent novas, recently published a paper detailing mass transfer dynamics within the binary system, based on radial velocity data from the HERMES spectrometer on the 1.2-meter Mercator telescope in La Palma, Chile. Radial velocity measurements relate to the Doppler shifts in the spectral lines of the stars and the material moving between the red giant, the accretion disk, and the white dwarf.
Planquart commented to Space.com that, “Jean Schneider has suggested the presence of a third companion in an eccentric orbit with a period of 80 years. Such additional orbital motion is, however, not detected in our decade-long radial-velocity monitoring.”
These radial velocity analyses have not provided evidence of a third stellar object, although Planquart acknowledges the possibility of a lower-mass body, such as a large exoplanet, remaining undetected.
Jeremy Shears, Director of the British Astronomical Association’s Variable Star Section, also expressed reservations. “Most astronomers are skeptical about this prediction, as am I,” Shears stated to Space.com. “The most prudent approach is to continue monitoring the system every clear night.”
Accretion Disk Dynamics and Nova Prediction
If the third object hypothesis is incorrect, and the pattern in nova timings observed by Schneider is merely coincidence, alternative explanations for T CrB’s behavior are needed.
Planquart’s observational data offers insights into the brightening observed in 1938 and 2015, followed by the dimming, most recently in 2023.
“We determined that from 2015 to 2023, the accretion disk surrounding the white dwarf reached its maximal extent, becoming hotter and more luminous, leading to increased brightness,” Planquart explained. This intensified the “matter-stealing effect,” accelerating the transfer of material to the white dwarf during a “super-active phase.” Subsequently, in 2023, the accretion disk cooled, resulting in the observed dimming, although material transfer to the white dwarf continues at a reduced rate.
“It is probable that this enhanced activity is necessary to initiate the nova explosion, as it enables material to accumulate more rapidly,” Planquart suggested.
However, details concerning the transition of the accretion disk into this super-active phase, and the precise processes occurring on the white dwarf’s surface between disk cooling and the nova explosion, remain somewhat uncertain.
Anticipating the Next Great Eruption
While Schneider’s specific date predictions may or may not materialize, the pattern of a super-active phase followed by quiescence and dimming strongly suggests that the nova is imminent. “We might expect to see the explosion in the coming months — or possibly next year,” Planquart concluded.
When the nova occurs, observers can anticipate a spectacular display. In 1946, T CrB reached magnitude +2, becoming easily visible to the naked eye, with brightness comparable to stars in the Big Dipper. Shears anticipates a similar level of brightness in the upcoming event.
Observing the Blaze Star
T CrB is located within the constellation Corona Borealis, the Northern Crown, currently observable across the Northern Hemisphere and as far south as South Africa and Australia (though lower on the horizon from more southerly locations).
“Currently, T CrB is at tenth magnitude, visible only through large binoculars,” Shears noted. “But as it brightens, it will become visible first in standard binoculars and then to the naked eye.”
The brightening will be swift. “The rise in brightness takes only a matter of hours — the exact duration is unknown as the initial brightening has never been observed directly,” Shears explained. “This is what makes this event so exciting. We hope that with numerous observers this time, we might indeed witness its awakening from dormancy.”
Indeed, a multitude of observers will be poised to witness this rare nova and gain deeper insights into the processes driving these gigantic thermonuclear explosions on white dwarf surfaces. “When it explodes, it will become one of the most extensively observed objects, targeted by telescopes worldwide,” Planquart affirmed.
Long-Term Fate of T Corona Borealis
Looking further ahead, an even more cataclysmic event awaits T CrB. The white dwarf’s mass in the T CrB system is calculated to be 1.37 times the mass of our sun. This is alarmingly close to the Chandrasekhar limit of 1.44 solar masses – the critical threshold at which a white dwarf undergoes runaway thermonuclear detonation, resulting in a Type Ia supernova. As the white dwarf continually accumulates mass from its red giant companion, it inches closer to this limit, accelerating its eventual self-destruction.
As Ken Hinkle, an astronomer at NOIRLab in Tucson, Arizona, explained to Space.com, “As white dwarfs approach the Chandrasekhar limit their radius shrinks and their surface gravity is increased. This results in the short time between eruptions.”
As the white dwarf nears the Chandrasekhar limit, nova events will likely become more frequent, leading to an eventual supernova explosion. However, this catastrophic event is projected to be hundreds of thousands, if not millions, of years in the future. In the meantime, astronomers and enthusiasts alike will continue to monitor the skies for the next nova outburst from T Corona Borealis.