T Coronae Borealis

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T Coronae Borealis
TCrBLocation.png
Location of T Coronae Borealis (circled in red)
Observation data
Epoch J2000       Equinox ICRS
Constellation Corona Borealis
Right ascension 15h 59m 30.1622s [1]
Declination +25° 55′ 12.613″ [1]
Apparent magnitude  (V)2.0–10.8 [2]
Characteristics
Evolutionary stage Red giant + white dwarf [3]
Spectral type M3III+p [4]
Variable type recurrent nova [2]
Astrometry
Radial velocity (Rv)−27.75±0.04 [5] km/s
Proper motion (μ)RA: −4.461 mas/yr [1]
Dec.: 12.016 mas/yr [1]
Parallax (π)1.0920±0.0275  mas [1]
Distance 2,990 ± 80  ly
(920 ± 20  pc)
Absolute magnitude  (MV)+0.16 (min.) [6]
Orbit [5]
Period (P)227.5528±0.0002 days
Semi-major axis (a)0.960 AU
Eccentricity (e)0.009±0.003 [7]
Inclination (i)61.5°
Periastron epoch (T)2459978.37±0.08
Semi-amplitude (K1)
(primary)		23.90±0.05 km/s
Details
Red giant
Mass 0.93 [5]   M☉
Radius 69±5 [8]   R☉
Luminosity 583±4 [9]   L☉
Surface gravity (log g)0.672+0.009
−0.007 [9]   cgs
Temperature 3,561±3 [9]   K
Metallicity [Fe/H]+0.20+0.05
−0.03 [9]   dex
Rotational velocity (v sin i)4.75±0.26 [5]  km/s
White dwarf
Mass 1.35 [5]   M☉
Radius 0.0045 [10]   R☉
Luminosity~100 [11]   L☉
Other designations
Blaze Star, T CrB, AAVSO 1555+26, BD+26°2765, HD 143454, HIP 78322, HR 5958, SAO 84129, 2MASS J15593015+2555126 [12]
Database references
SIMBAD data

T Coronae Borealis is a binary star and a recurrent nova about 3,000 light-years (920 parsecs ) away in the constellation Corona Borealis. [13] Its apparent magnitude varies between 2.0 in outburst and 10.8 in quiescence, representing about a 3300-fold change in brightness. T Coronae Borealis is its variable-star designation and the name most frequently used in the astronomical literature, but it also has the official proper name Blaze Star. The system was first observed in outburst in 1866 by John Birmingham, [14] but had been observed earlier in quiescence as an unremarkable 10th magnitude star. [15] It may have been observed in 1217 and in 1787 as well. [16] [17] Its February 1946 flare-up was discovered independently by three observers: the Soviet amateur astronomer A. S. Kamenchuk, the 15-year-old schoolboy Michael Woodman from Wales, and the British variable star observer N. F. H. Knight. [18] This led to the guess that the star flares every 80 years [19] with the next nova outburst then predicted to occur before 2027. T Coronae Borealis enters solar conjunction in late November and becomes hidden by the Sun's glare for a few months.

Contents

Nomenclature

T Coronae Borealis (abbreviated T CrB or unofficially T Cor Bor) [20] is the star's variable star designation and is its most commonly used name. It also has the Bright Star Catalogue designation HR 5958 and the Henry Draper Catalogue designation HD 143454. [12]

The proper name Blaze Star [21] has been used since its outburst in 1866, and was officially approved by the IAU Working Group on Star Names on 22 September 2025. [22]

Description

The light curve of T Coronae Borealis during the time surrounding its 1946 eruption, plotted from AAVSO data TCrBLightCurve.png
The light curve of T Coronae Borealis during the time surrounding its 1946 eruption, plotted from AAVSO  data

T CrB normally has a magnitude of about 10, which is near the limit of typical binoculars. Two well-documented outbursts have been observed, reaching magnitude 2.0 on May 12, 1866 and magnitude 3.0 on February 9, 1946, [23] though a more recent paper shows the 1866 outburst with a possible peak range of magnitude 2.5±0.5. [24] When at peak magnitude of 2.5, this recurrent nova is dimmer than about 100  brightest stars in the night sky, [25] but easily visible to the naked eye.

Diagram of T Coronae Borealis based on a description given by Kraft using the updated mass ratio given by Stanishev TCrBsketch.png
Diagram of T Coronae Borealis based on a description given by Kraft using the updated mass ratio given by Stanishev

Like all novae, 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. [3] The hot component, which initially was the most massive and brightest of the two stars, is now 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 overall luminosity of the system increases by orders of magnitude. [11] [26] [27] [28]

T Coronae Borealis imaged on 23 June 2026 with a Unistellar 114mm smart telescope (north is towards top right, field of view about 0.5deg) T CrB-2026Jun23.png
T Coronae Borealis imaged on 23 June 2026 with a Unistellar 114mm smart telescope (north is towards top right, field of view about 0.5°)
AAVSO light curve of recurrent nova T CrB from Jan 1, 2008 to Nov 17, 2010, showing rotating ellipsoidal variability. Up is brighter and down is fainter. Day numbers are Julian day. T-CrB-Lightcurve-AAVSO.gif
AAVSO light curve of recurrent nova T CrB from Jan 1, 2008 to Nov 17, 2010, showing rotating ellipsoidal variability. Up is brighter and down is fainter. Day numbers are Julian day.

The two components of the system orbit each other every 227.5528 d. The orbit is almost circular and is inclined at an angle of 61.5°. The separation between the components is 0.960  AU. [5]

2016–present activity

On April 20, 2016, Sky & Telescope reported a sustained brightening since February 2015 from magnitude 10.5 to about 9.2. A similar event was reported in 1938, 8 years before the 1946 outburst. [29] By June 2018, the star had dimmed slightly but still remained at an unusually high level of activity. By mid-2023, it had faded by 0.35 magnitude or about 28%; [a] its lowest brightness seen since 2016. [30] A similar dimming occurred in the year before the 1946 outburst, [31] leading some to predict an eruption before September 2024. [32] The eruption has repeatedly been predicted to be imminent, but no nova has been observed as of October2026 and several of the predictions have already lapsed. [31]

After the 2023–2024 fading event, T CrB brightened around May 2024, but again by July 2026 its light curve showed renewed decline. Hence, some researchers opine that If the decline continues, then this may actually be a truer analogue to the similar pre-1946 dip, instead of the 2023–2024 dip event considered in earlier predictions and hence, an eruption around December 2026 may still be possible. [33]

Outburst predictions

Predictions of the next nova (in order of when the prediction was made):

  • 2026–2027 (made in 1946 either by N. F. H. Knight or W. M. Lindley) [34]
  • Mid‐February 2024 to end‐September 2026 (made in March 2023) [35] (lapsed)
  • Beginning January 2024 to mid-August 2024 (made in June 2023) [36] (lapsed)
  • January 2024 (made in August 2023) [37] (lapsed)
  • End of October 2024 (made in June 2024) [38] (lapsed)
  • Around March 27, 2025 (lapsed); November 10, 2025 (lapsed); June 25, 2026 (lapsed); or February 8, 2027 ± 8 days (made in October 2024) [39]
  • Around March 5, 2027, between February 2027 and May 2027, up to November 2027 (made in October 2026) [40]

Notes

  1. ↑

References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. 1 2 3 Kraft, Robert P. (1958). "The Binary System Nova T Coronae Borealis". Astrophysical Journal . 127. University of Chicago Press: 625. Bibcode:1958ApJ...127..625K. doi: 10.1086/146495 . ISSN   0004-637X.
  4. ↑ Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports . 55 (1). MAIK Nauka/Interperiodica: 31–81. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070. ISSN   1063-7729. LCCN   93646197. OCLC   43712703. S2CID   122700080. CODEN   ATROES.
  5. 1 2 3 4 5 6 Munari, U.; Walter, F.; Masetti, N.; Valisa, P.; Dallaporta, S.; Bergamini, A.; Cherini, G.; Frigo, A.; Maitan, A. (July 31, 2025). "T CrB: overview of the accretion history, Roche-lobe filling, orbital solution, and radiative modeling". Astronomy and Astrophysics. 701: A176. arXiv: 2507.23323 . Bibcode:2025A&A...701A.176M. doi: 10.1051/0004-6361/202555917 .
  6. ↑ Nikolov, Yanko (2022). "Interstellar polarization and extinction toward the Recurrent Nova T CRB". New Astronomy . 97 101859. Elsevier. arXiv: 2201.11521 . Bibcode:2022NewA...9701859N. doi:10.1016/j.newast.2022.101859. ISSN   1384-1092. OCLC   123402017.
  7. ↑ Planquart, Léa; Jorissen, Alain; Van Winckel, Hans (2025). "Resolving the mass transfer in the symbiotic recurrent nova T Coronae Borealis". Astronomy and Astrophysics . 694. EDP Sciences: A85. arXiv: 2501.02984 . Bibcode:2025A&A...694A..85P. doi: 10.1051/0004-6361/202452833 . ISSN   0004-6361. LCCN   74220573. OCLC   1518497. CODEN   AAEJAF.
  8. ↑ Norris, Ryan; Anugu, Narsireddy; Gaudin, Thomas; Otulakowska-Hypka, Magdalena; Kaczmarek, Fabian; Caruso, Cameron; Gustafson, Cody; Kotowski, Andrew; Proni, Rebecca; Roy, Nirupam; Baron, Fabien; Banerjee, Dipankar P. K.; Baylis-Aguirre, Dana K.; Creech-Eakman, Michelle J.; Linford, Justin (June 10, 2026). "Pre-nova Observations of T CrB: A view from the CHARA Array". The Astrophysical Journal Letters. 1004 (1): L13. arXiv: 2606.17272 . Bibcode:2026ApJ..1004L..13N. doi: 10.3847/2041-8213/ae71d0 . ISSN   2041-8205.
  9. 1 2 3 4 Hinkle, Kenneth H.; Nagarajan, Pranav; Fekel, Francis C.; Mikołajewska, Joanna; Straniero, Oscar; Muterspaugh, Matthew W. (2025). "Binary Parameters for the Recurrent Nova T Coronae Borealis". The Astrophysical Journal . 983 (1). IOP Publishing: 76. arXiv: 2502.20664 . Bibcode:2025ApJ...983...76H. doi: 10.3847/1538-4357/adbe63 . ISSN   1538-4357.
  10. ↑ Schlindwein, Wagner; Baptista, Raymundo; Luna, Gerardo Juan Manuel (2025). "Modeling the High-brightness State of the Recurrent Nova T CRB as an Enhanced Mass-transfer Event". The Astrophysical Journal . 989 (1). IOP Publishing: 78. arXiv: 2506.05098 . Bibcode:2025ApJ...989...78S. doi: 10.3847/1538-4357/ade98c . ISSN   1538-4357.
  11. 1 2 3 Stanishev, V.; Zamanov, R.; Tomov, N.; Marziani, P. (2004). "Hα variability of the recurrent nova T Coronae Borealis". Astronomy and Astrophysics . 415 (2). EDP Sciences: 609–616. arXiv: astro-ph/0311309 . Bibcode:2004A&A...415..609S. doi: 10.1051/0004-6361:20034623 . ISSN   0004-6361. LCCN   74220573. OCLC   1518497. S2CID   3000175. CODEN   AAEJAF.
  12. 1 2 "T CrB". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved December 30, 2025.
  13. ↑ Andrews, Robin George (March 8, 2024). "The Night Sky Will Soon Get 'a New Star.' Here's How to See It". The New York Times . ISSN   1553-8095. LCCN   sn78004456. OCLC   1645522 . Retrieved March 9, 2024.{{cite news}}: CS1 maint: deprecated archival service (link)
  14. ↑ Pettit, Edison (1946). "The Light-Curves of T Coronae Borealis". Publications of the Astronomical Society of the Pacific . 58 (341): 153. Bibcode:1946PASP...58..153P. doi: 10.1086/125797 . ISSN   1538-3873. OCLC   40768120.
  15. ↑ Barnard, E. E. (1907). "Nova T Coronae of 1866". Astrophysical Journal . 25. University of Chicago Press: 279. Bibcode:1907ApJ....25..279B. doi: 10.1086/141446 . ISSN   0004-637X.
  16. ↑ Schaefer, Bradley E. (November 16, 2023). Evans, James (ed.). "The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD". Journal for the History of Astronomy . 54 (4). SAGE Publishing: 436–455. arXiv: 2308.13668 . Bibcode:2023JHA....54..436S. doi:10.1177/00218286231200492. ISSN   0021-8286. LCCN   73618135. OCLC   645363374.
  17. ↑ Thompson, Joanna (September 15, 2023). McNamara, Alexander; Ghose, Tia; Specktor, Brandon (eds.). "Evidence of mysterious 'recurring nova' that could reappear in 2024 found in medieval manuscript from 1217". Live Science . Future plc . Retrieved March 21, 2024.
  18. ↑ Shears, Jeremy (2026). "Two independent British discoveries of the 1946 eruption of T Coronae Borealis". Journal of the British Astronomical Association. 136 (2): 91–98. doi:10.64150/869rwd. ISSN   0007-0297.
  19. ↑ Morelle, Rebecca; Francis, Alison (December 30, 2024). "Astronomers ready for dazzling but brief celestial show after 80-year wait". BBC News . Archived from the original on January 25, 2025.
  20. ↑ Starrfield, Sumner; Bose, Maitrayee; Woodward, Charles E.; Perron, Isabelle; Shaw, Gargi; Evans, Aneurin; Iliadis, Christian; Hix, W. Raphael (June 1, 2024). "The evolution leading to a thermonuclear runaway". Bulletin of the American Astronomical Society . 56 (7): 132.01. Bibcode:2024AAS...24413201S. ISSN   0002-7537. OCLC   1479434.
  21. ↑ Proctor, Mary (June 1897). "Heavens for June". Popular Astronomy . 5: 104–105. Bibcode:1897PA......5...97P.
  22. ↑ "IAU Catalog of Star Names" . Retrieved September 23, 2025.
  23. ↑ Sanford, Roscoe F. (1949). "High-Dispersion Spectrograms of T Coronae Borealis". Astrophysical Journal . 109. University of Chicago Press: 81. Bibcode:1949ApJ...109...81S. doi: 10.1086/145106 . ISSN   0004-637X.
  24. ↑ Schaefer, Bradley E. (2010). "Comprehensive Photometric Histories of All Known Galactic Recurrent Novae". The Astrophysical Journal Supplement Series . 187 (2). IOP Publishing: 275–373. arXiv: 0912.4426 . Bibcode:2010ApJS..187..275S. doi:10.1088/0067-0049/187/2/275. S2CID   119294221.
  25. ↑ "Vmag<2.5". SIMBAD Astronomical Database . Retrieved June 25, 2010.
  26. ↑ Linford, Justin D.; Chomiuk, Laura; Sokoloski, Jennifer L.; Weston, Jennifer H. S.; Van Der Horst, Alexander J.; Mukai, Koji; Barrett, Paul; Mioduszewski, Amy J.; Rupen, Michael (2019). "T CRB: Radio Observations during the 2016-2017 "Super-active" State". The Astrophysical Journal . 884 (1). IOP Publishing: 8. arXiv: 1909.13858 . Bibcode:2019ApJ...884....8L. doi: 10.3847/1538-4357/ab3c62 . ISSN   1538-4357. S2CID   203593955.
  27. ↑ Iłkiewicz, Krystian; Mikołajewska, Joanna; Stoyanov, Kiril; Manousakis, Antonios; Miszalski, Brent (2016). "Active phases and flickering of a symbiotic recurrent nova T CrB". Monthly Notices of the Royal Astronomical Society . 462 (3): 2695. arXiv: 1607.06804 . Bibcode:2016MNRAS.462.2695I. doi: 10.1093/mnras/stw1837 . S2CID   119104759.
  28. ↑ Luna, GJM; Mukai, K.; Sokoloski, J. L.; Nelson, T.; Kuin, P.; Segreto, A.; Cusumano, G.; Jaque Arancibia, M.; Nuñez, N. E. (2018). "Dramatic change in the boundary layer in the symbiotic recurrent nova T Coronae Borealis". Astronomy and Astrophysics . 619 (1). EDP Sciences: 61. arXiv: 1807.01304 . Bibcode:2018A&A...619A..61L. doi: 10.1051/0004-6361/201833747 . ISSN   0004-6361. LCCN   74220573. OCLC   1518497. S2CID   119078482. CODEN   AAEJAF.
  29. ↑ King, Bob (April 20, 2016). Tyson, Peter (ed.). "Is T CrB About to Blow its Top?". Sky & Telescope . F+W Media. ISSN   0037-6604. OCLC   1765612. Archived from the original on August 5, 2020. Retrieved August 6, 2017.
  30. ↑ Schaefer, B.E.; Kloppenborg, B.; Waagen, E.O.; et al. (The AAVSO Observers) (n.d.). "Announcing T CrB pre-eruption dip". American Association of Variable Star Observers . Cambridge, MA. Retrieved January 18, 2024.
  31. 1 2 Pearson, Ezzy; Lintott, Chris (June 23, 2025). Bramley, Chris; Marsh, Steve; Pearson, Ezzy; Wilder, Jess; Todd, Iain (eds.). "T Coronae Borealis 'Blaze Star' nova event". BBC Sky at Night Magazine . Immediate Media. ISSN   1745-9869. OCLC   904019019 . Retrieved September 10, 2025.
  32. ↑ Ridgeway, Beth (June 6, 2024). "NASA, Global Astronomers Await Rare Nova Explosion". Marshall Space Center . NASA . Retrieved July 23, 2024.
  33. ↑ Pei, Songpeng; Zhang, Xiaowan; Su, Renzhi; Ou, Ziwei; Cai, Yongzhi; Li, Qiang; Liu, Yu; Ren, Xiaoqin; Yang, Taozhi (2026). "When will T Coronae Borealis next erupt as a nova? Constraints from recurrence, orbital phase, and accretion-state evolution". Monthly Notices of the Royal Astronomical Society. 550 (4) stag1361. doi: 10.1093/mnras/stag1361 .
  34. ↑ Shears, J. H. (June 1, 2024). "An Independent Discovery of the 1946 Eruption of the Recurrent Nova T Coronae Borealis and an Early Prediction of a Future Outburst". Research Notes of the American Astronomical Society . 8 (6): 157. Bibcode:2024RNAAS...8..157S. doi: 10.3847/2515-5172/ad566b . ISSN   2515-5172.
  35. ↑ Schaefer, Bradley E. (September 1, 2023). "The B & V light curves for recurrent nova T CrB from 1842-2022, the unique pre- and post-eruption high-states, the complex period changes, and the upcoming eruption in 2025.5 ± 1.3". Monthly Notices of the Royal Astronomical Society . 524 (2): 3146–3165. arXiv: 2303.04933 . Bibcode:2023MNRAS.524.3146S. doi: 10.1093/mnras/stad735 . ISSN   0035-8711.
  36. ↑ Schaefer, Bradley E.; Kloppenborg, Brian; Waagen, Elizabeth O.; et al. (The AAVSO Observers) (June 1, 2023). "Recurrent nova T CrB has just started its Pre-eruption Dip in March/April 2023, so the eruption should occur around 2024.4 +- 0.3". The Astronomer's Telegram (16107): 1. Bibcode:2023ATel16107....1S.
  37. ↑ Maslennikova, N. A.; Tatarnikov, A. M.; Tatarnikova, A. A.; Dodin, A. V.; Shenavrin, V. I.; Burlak, M. A.; Zheltoukhov, S. G.; Strakhov, I. A. (October 1, 2023). "Recurrent Symbiotic Nova T Coronae Borealis before Outburst". Astronomy Letters . 49 (9): 501–515. arXiv: 2308.10011 . Bibcode:2023AstL...49..501M. doi:10.1134/S1063773723090037. ISSN   1063-7737.
  38. ↑ Toalá, Jesús A.; González-Martín, Omaira; Sacchi, Andrea; Vasquez-Torres, Diego A. (August 1, 2024). "The X-ray rise and fall of the symbiotic recurrent nova system T CrB". Monthly Notices of the Royal Astronomical Society . 532 (2): 1421–1433. arXiv: 2405.08980 . Bibcode:2024MNRAS.532.1421T. doi: 10.1093/mnras/stae1579 . ISSN   0035-8711.
  39. ↑ Schneider, Jean (October 2024). "When will the Next T CrB Eruption Occur?". Research Notes of the American Astronomical Society . 8 (10): 272. Bibcode:2024RNAAS...8..272S. doi: 10.3847/2515-5172/ad8bba . ISSN   2515-5172.
  40. ↑ Binder, Alan; Graun, Kenneth (October 2026). "Empirical Studies of the Timing of Nova Events of the Recurring Nova, T Coronae Borealis". Research Notes of the AAS. 10 (10). The American Astronomical Society: 306. doi: 10.3847/2515-5172/aeb886 . ISSN   2515-5172.

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