Theta Delphini

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Theta Delphini
Diagram showing star positions and boundaries of the Delphinus constellation and its surroundings
Cercle rouge 100%.svg
Location of θ Delphini (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Delphinus
Right ascension 20h 38m 43.98687s[1]
Declination +13° 18′ 54.4484″[1]
Apparent magnitude (V) 5.71[2]
Spectral type K3Ib[3]
U−B color index +1.71[4]
B−V color index +1.52[4]
Radial velocity (Rv)-15.09[5] km/s
Proper motion (μ) RA: 3.53[1] mas/yr
Dec.: -0.47[1] mas/yr
Parallax (π)1.5887 ± 0.0738[6] mas
Distance2,050 ± 100 ly
(630 ± 30 pc)
Mass5.69[7] M
Radius88±25[8] R
Diameter88±25[8] D
Luminosity3,780[6] L
Surface gravity (log g)1.3[9] cgs
Temperature4,203[6] K
Metallicity [Fe/H]+0.22[9] dex
Rotational velocity (v sin i)3.0[10] km/s
Other designations
θ Del, 8 Del, BD+12° 4411, HD 196725, HIP 101882, SAO 106342, HR 7892, GC 28743[11]
Database references

Theta Delphini (θ Del, θ Delphini) is a star in the constellation Delphinus. It has an apparent magnitude of about 5.7, meaning that it is just barely visible to the naked eye under excellent viewing conditions. Based upon parallax measurements made by the Hipparcos spacecraft, this star is around 1300 light years away from the Sun.[1]

Theta Delphini's spectral type is K3Ib, meaning it is an K-type supergiant.[12] These types of stars form when relatively massive (10 to 30 M) stars like B-type main sequence stars run out of hydrogen to fuse and start cooling down.[13] It has been described as a super-metal-rich star because of its high metallicity[9]


  1. 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR On-line Data Catalog. Bibcode 2002yCat.2237....0D.
  3. Bidelman, William P. (1951). "Spectral Classification of Stars Listed in Miss Payne's Catalogue of C Stars". The Astrophysical Journal 113: 304. Bibcode 1951ApJ...113..304B.
  4. 4.0 4.1 Fernie, J. D. (1983). "New UBVRI photometry for 900 supergiants". Astrophysical Journal Supplement Series 52: 7–22. Bibcode 1983ApJS...52....7F. doi:10.1086/190856.
  5. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics 430: 165–186. Bibcode 2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  6. 6.0 6.1 6.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. arXiv:1804.09365. Bibcode 2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (2010). "Masses and luminosities of O- and B-type stars and red supergiants". Astronomische Nachrichten 331 (4): 349. Bibcode 2010AN....331..349H.
  8. Van Belle, G. T.; Creech-Eakman, M. J.; Hart, A. (2009). "Supergiant temperatures and linear radii from near-infrared interferometry". Monthly Notices of the Royal Astronomical Society 394 (4): 1925. Bibcode 2009MNRAS.394.1925V.
  9. 9.0 9.1 9.2 Malagnini, M. L.; Morossi, C.; Buzzoni, A.; Chavez, M. (2000). "Observations and Atmospheric Parameters of Super-Metal-rich Candidates". Publications of the Astronomical Society of the Pacific 112 (777): 1455. Bibcode 2000PASP..112.1455M.
  10. De Medeiros, J. R.; Udry, S.; Burki, G.; Mayor, M. (2002). "A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars". Astronomy and Astrophysics 395: 97–98. Bibcode 2002A&A...395...97D. doi:10.1051/0004-6361:20021214.
  11. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  12. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  13. Ekström, S.; Georgy, C.; Eggenberger, P.; Meynet, G.; Mowlavi, N.; Wyttenbach, A.; Granada, A.; Decressin, T. et al. (2012). "Grids of stellar models with rotation. I. Models from 0.8 to 120 M⊙ at solar metallicity (Z = 0.014)". Astronomy & Astrophysics 537: A146. arXiv:1110.5049. Bibcode 2012A&A...537A.146E. doi:10.1051/0004-6361/201117751.

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