T Coronae Borealis (''T CrB''), nicknamed the Blaze Star, is a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

and a recurrent

nova A nova ( novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months. All observed novae involve white ...

about away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Corona Borealis Corona Borealis is a small constellation in the Northern Celestial Hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Its brightest stars form a sem ...

. It was first discovered in outburst in 1866 by

John Birmingham John Birmingham (born 7 August 1964) is a British-born Australian author, known for the 1994 memoir ''He Died with a Felafel in His Hand'', the ''Axis of Time'' trilogy, and the well-received space opera series, the ''Cruel Stars'' trilogy. ...

, though it had been observed earlier in quiescence as a 10th magnitude star. It may have been observed in 1217 and in 1787 as well. In February 1946, 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 A flare, also sometimes called a fusée, fusee, or bengala, bengalo in several European countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illuminatio ...

every 80 years.

Description

T CrB normally has a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of about 10, which is near the limit of typical binoculars. Well documented outbursts have been seen twice, reaching magnitude 2.0 on May 12, 1866 and magnitude 3.0 on February 9, 1946, though a more recent paper shows the 1866 outburst with a possible peak range of magnitude 2.5 ± 0.5. Even when at peak magnitude of 2.5, this

recurrent nova A nova ( novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months. All observed novae involve white ...

is dimmer than about 120 brightest stars in the night sky. It is sometimes nicknamed the ''Blaze Star''. TCrBsketch

T CrB is a

binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...

containing a large cool component and a smaller hot component. The cool component is a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...

that transfers material to the hot component. The hot component is a

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

surrounded by an

accretion disc An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is most frequently a star. Friction, uneven irradiance, magnetohydrodynamic effects, and ...

, 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 M3 giant. The hot component contributes some emission and dominates the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

output. During outbursts, the transfer of material to the hot component increases greatly, the hot component expands, and the luminosity of the system increases. T-CrB-Lightcurve-AAVSO

The two components of the system orbit each other about every 228 days. The orbit is almost circular and is inclined at an angle of 67°. The radius of primary component orbit around the center of mass is .

2016–present activity

On 20 April 2016, the ''

Sky & Telescope ''Sky & Telescope'' (''S&T'') is a monthly magazine covering all aspects of amateur and professional astronomy, including what to see in the sky tonight and new findings in astronomy. Other topics covered include: *observing guides for planets, ...

'' website reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2. A similar event was reported in 1938, followed by another outburst in 1946. By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity. By mid-2023, it faded by 0.35 magnitude or about 28 percent; the lowest brightness seen since 2016. A similar dimming occurred in the year before the 1946 outburst, suggesting an eruption before September 2024. As of , such a nova has not yet been observed, although some have predicted it is imminent. Predictions of the next nova: * 2026-2027 (made in 1946 either by N. F. H. Knight or W. M. Lindley) * Mid February 2024 to end September 2026 (made in March 2023) * Beginning January 2024 to mid August 2024 (made in June 2023) (lapsed) * January 2024 (made in August 2023) (lapsed) * End of October 2024 (made in June 2024) (lapsed) * Around 27 March 2025 (lapsed), 10 November 2025, 25 June 2026 or 8 February 2027 (made in October 2024)

Notes

References

External links

www.daviddarling.info * AAVSO
Check Recent Observations
(get recent magnitude estimates for T CrB) {{DEFAULTSORT:T Coronae Borealis Recurrent novae Corona Borealis 143454 Coronae Borealis, T M-type giants 18660512 BD+26 2765 J15593015+2555126 White dwarfs 078322

Description

2016–present activity

Notes

References

Further reading

External links