T Coronae Borealis (''T CrB''), is a recurring

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

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 origins of the e ...

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 se ...

. 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'', and his ''Axis of Time'' trilogy. Early life and education Birmingham was born in Liverpool, United ...

, although it had been observed earlier as a 10th magnitude star.

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. It has been seen to outburst twice, reaching magnitude 2.0 on May 12, 1866 and magnitude 3.0 on February 9, 1946, although 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 (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramati ...

is dimmer than about 120 stars in the night sky. It is sometimes nicknamed the ''Blaze Star''.A Digital Spectral Classification Atlas, R. O. Gray
34. Unusual Stellar Spectra III: two emission-line stars T CrB is a

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

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 outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

which is transferring material to the hot component. The hot component is a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

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

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

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 every 228 days. The orbit is almost circular and is inclined at an angle of 67°. The stars are separated by .

2016-present activity

On 20 April 2016, the

Sky and Telescope ''Sky & Telescope'' (''S&T'') is a monthly American magazine covering all aspects of amateur astronomy, including the following: *current events in astronomy and space exploration; *events in the amateur astronomy community; *reviews of astronomi ...

website reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2. A similar event was reported in 1938, shortly before the 1946 outburst. By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity. Since then, according to observations sent to the AAVSO, the star has hovered around magnitude 10.0.

References

External links

* http://www.daviddarling.info/encyclopedia/B/Blaze_Star.html * AAVSO
Quick Look View of AAVSO 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 Astronomical events in the near future

Description

2016-present activity

References

Further reading

External links