Winnecke 4

Winnecke 4 (also known as Messier 40 or WNC 4) is an optical double star consisting of two unrelated stars in a northerly zone of the sky, Ursa Major.

Winnecke 4

Winnecke 4 double star
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
A
Right ascension 12h 22m 12.5278s[1]
Declination +58° 4′ 58.539″[1]
Apparent magnitude (V) 9.64[2]
B
Right ascension 12h 22m 18.9989s[1]
Declination +58° 5′ 10.364″[1]
Apparent magnitude (V) 10.11[2]
Characteristics
A
Spectral type K0 III[3]
B
Spectral type G0 V[3]
Astrometry
A
Parallax (π)2.87 ± 0.24[1] mas
Distance1,140 ± 100 ly
(350 ± 30 pc)
Absolute magnitude (MV)+0.88[3]
B
Parallax (π)7.13 ± 0.24[1] mas
Distance460 ± 20 ly
(140 ± 5 pc)
Absolute magnitude (MV)+4.0[3]
Details
A
Mass1.1[3] M☉
B
Mass1.2[3] M☉
Other designations
M40, WNC 4, BD+56 1372, CCDM 12223+5805, WDS J12222+5805
A: HD 238107, SAO 28353
B: HD 238108, SAO 28355
Database references
SIMBADdata

The pair were discovered by Charles Messier in 1764 while he was searching for a nebula that had been reported in the area by Johannes Hevelius. Not seeing any nebulae, Messier catalogued this apparent pair instead. The pair were rediscovered by Friedrich August Theodor Winnecke in 1863, and included in the Winnecke Catalogue of Double Stars as number 4. Burnham calls M40 "one of the few real mistakes in the Messier catalog," faulting Messier for including it when all he saw was a double star, not a nebula of any sort.[4]

In 1991 the separation between the components was measured at 51.7″, an increase since 1764. Data gathered by astronomers Brian Skiff (2001) and Richard L. Nugent (2002) strongly suggested the subject was merely an optical double star rather than a physically connected (binary) system.[3] In 2016, parallax measurements from the Gaia satellite showed the stars involved (HD 238107 and HD 238108) are indeed unrelated.[5] As measured by Gaia, star A is 350 ± 30 parsecs (1,142 ± 98 light-years) and star B is 140 ± 6 parsecs (457 ± 20 light-years) away. Thus the A star that seems the brighter is over twice as far as B.[5]

References
  1. Gaia Collaboration; Brown, A. G. A; Vallenari, A; Prusti, T; De Bruijne, J. H. J; Mignard, F; Drimmel, R; Babusiaux, C; Bailer-Jones, C. A. L; Bastian, U; Biermann, M; Evans, D. W; Eyer, L; Jansen, F; Jordi, C; Katz, D; Klioner, S. A; Lammers, U; Lindegren, L; Luri, X; O'Mullane, W; Panem, C; Pourbaix, D; Randich, S; Sartoretti, P; Siddiqui, H. I; Soubiran, C; Valette, V; Van Leeuwen, F; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512.
  2. Astronomy and Astrophysics, volume 355, L27-30 (2000/3-2) "The Tycho-2 catalogue of the 2.5 million brightest stars." HOG E. et al.
  3. Nugent, Richard L (2002). "The Nature of the Double Star M40". Journal of the Royal Astronomical Society of Canada. 96: 63. Bibcode:2002JRASC..96...63N.
  4. Robert Burnham (1978). Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System. Courier Corporation. p. 1982. ISBN 978-0-486-23673-5.
  5. Merrifield, M. R; Gray, M. E; Haran, B (2017). "Gaia Shows that Messier 40 is Definitely Not a Binary Star". The Observatory. 137: 23. arXiv:1612.00834. Bibcode:2017Obs...137...23M.


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