T Coronae Borealis Explained

T Coronae Borealis should not be confused with Tau Coronae Borealis.

T Coronae Borealis (T CrB), nicknamed the Blaze Star, is a binary star and a recurrent nova in the constellation Corona Borealis.[1] It was first discovered in outburst in 1866 by John Birmingham,[2] though it had been observed earlier as a 10th magnitude star.[3] It may have been observed in 1217 and in 1787 as well.[4] [5] It is expected to undergo an outburst again, likely during August 2024.[6]

Description

T CrB normally has a magnitude 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 is dimmer than about 120 stars in the night sky.[7] It is sometimes nicknamed the Blaze Star.[8]

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 M3 giant. 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.

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 stars are separated by .

2016–present activity

On 20 April 2016, the Sky & Telescope 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.[9] 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; the lowest brightness seen since 2016.[10] A similar dimming occurred in the year before the 1946 outburst,[11] indicating an eruption before September 2024.[12]

Further reading

External links

Notes and References

  1. News: Andrews . Robin George . The Night Sky Will Soon Get 'a New Star.' Here's How to See It. - A nova named T Coronae Borealis lit up the night about 80 years ago, and astronomers say it's expected to put on another show in the coming months. . 8 March 2024 . . live . https://archive.today/20240308220630/https://www.nytimes.com/article/nova-new-star-t-coronae-borealis.html. 8 March 2024 . 9 March 2024 .
  2. 1946PASP...58..153P. The Light-Curves of T Coronae Borealis. Publications of the Astronomical Society of the Pacific. 58. 153. Pettit. Edison. 1946. 341. 10.1086/125797. free.
  3. 1907ApJ....25..279B. Nova T Coronae of 1866. Astrophysical Journal. 25. 279. Barnard. E. E.. 1907. 10.1086/141446.
  4. Schaefer . Bradley E. . 16 November 2023 . The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD . Journal for the History of Astronomy . en . 54 . 4 . 436–455 . 10.1177/00218286231200492 . 0021-8286. 2308.13668 . 2023JHA....54..436S .
  5. Web site: Thompson . Joanna . September 15, 2023 . Evidence of mysterious 'recurring nova' that could reappear in 2024 found in medieval manuscript from 1217 . 2024-03-21 . Live Science.
  6. Web site: Lyster . Tim . 1 May 2024 . The Jewel in the Crown . 2 July 2024 . AAVSO . American Association of Variable Star Observers .
  7. Web site: Vmag<2.5 . SIMBAD Astronomical Database . 2010-06-25.
  8. Proctor . Mary . June 1897 . Heavens for June . Popular Astronomy . 5 . 104–105 . 1897PA......5...97P . 2 July 2024.
  9. Web site: Is T CrB About to Blow its Top?. Sky & Telescope website. 20 April 2016. 2017-08-06.
  10. Web site: Schaefer . B.E. . Kloppenborg . B. . Waagen . E.O. . Announcing T CrB pre-eruption dip . AAVSO . American Association of Variable Star Observers . 18 January 2024.
  11. Web site: Todd . Ian . T Coronae Borealis nova event guide and how to prepare . Sky at Night Magazine . BBC . 18 March 2024.
  12. Web site: 2024-06-06 . NASA, Global Astronomers Await Rare Nova Explosion - NASA . 2024-07-23 . en-US.

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