T Coronae Borealis


T Coronae Borealis is a binary star and a recurrent nova about away in the constellation Corona Borealis. It has the official proper name Blaze Star, is the variable-star designation. The system was first observed in outburst in1866 by John Birmingham, though it had been observed earlier in quiescence as a 10thmagnitude star. It may have been observed in1217 and in1787 as well. In February1946, Michael Woodman, a 15-year-old schoolboy from Wales, observed a flare‐up, subsequently writing to the Astronomer Royal and leading to the theory that the star flares every 80years, with the next nova expected to occur before 2027.

Nomenclature

T Coronae Borealis is the star's variable star designation. It also has the Bright Star Catalogue designation HR 5958 and the Henry Draper Catalogue designation HD 143454.
The proper name Blaze Star has been used since its outburst in 1866, and was officially approved by the IAU Working Group on Star Names on 22 September 2025.

Description

T CrB normally has a magnitude of about10, which is near the limit of typical binoculars. Two well-documented outbursts have been observed, reaching magnitude2.0 on May12, 1866 and magnitude3.0 on February9, 1946, though a more recent paper shows the 1866outburst with a possible peak range of magnitude. Even when at peak magnitude of2.5, this recurrent nova is dimmer than about 100brightest stars in the night sky, but easily visible to the naked eye.
T CrB is a binary system containing a large cool component and a smaller hot component. The cool component is a red giant that transfers material to the hot component. The hot component is a white dwarf surrounded by an accretion disc, all hidden inside a dense cloud of material from the red giant. When the system is quiescent, the red giant dominates the visible light output and the system appears as an M3giant. The hot component contributes some emission and dominates the ultraviolet output. During outbursts, the transfer of material to the hot component increases greatly, the hot component expands, and the luminosity of the system increases by orders of magnitude.
The two components of the system orbit each other every. The orbit is almost circular and is inclined at an angle of61.5°. The radius of the orbit of the primary component around the center of mass is.

2016–present activity

On April 20, 2016, Sky & Telescope reported a sustained brightening since February2015 from magnitude10.5 to about9.2. A similar event was reported in1938, followed by another outburst in1946. By June2018, the star had dimmed slightly but still remained at an unusually high level of activity. By mid-2023, it had faded by0.35 magnitude or about 28%; its lowest brightness seen since2016. A similar dimming occurred in the year before the 1946outburst, leading some to predict an eruption before September2024. As of, such a nova has not yet been observed, although some have predicted it is imminent.

Outburst predictions

Predictions of the next nova :
  • 2026-2027
  • Mid‐February 2024 to end‐September2026
  • Beginning January 2024 to mid-August2024
  • January 2024
  • End of October2024
  • Around March27, 2025 ; November10, 2025 ; June25, 2026; or February8, 2027