Winnecke 4

Winnecke 4

Winnecke 4 double star
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
A
Right ascension 12h 22m 12.5272s[1]
Declination +58° 4′ 58.549″[1]
Apparent magnitude (V) 9.64[2]
B
Right ascension 12h 22m 18.9992s[3]
Declination +58° 5′ 10.366″[3]
Apparent magnitude (V) 10.11[2]
Characteristics
A
Spectral type K0 III[4]
B
Spectral type G0 V[4]
Astrometry
A
Parallax (π)3.2191 ± 0.0118 mas[1]
Distance1,013 ± 4 ly
(311 ± 1 pc)
Absolute magnitude (MV)+0.88[4]
B
Parallax (π)6.9328 ± 0.0155 mas[3]
Distance470 ± 1 ly
(144.2 ± 0.3 pc)
Absolute magnitude (MV)+4.0[4]
Details
A
Mass1.15[5] M☉
Radius4.48[6] R☉
Luminosity13[6] L☉
Surface gravity (log g)3.16[5] cgs
Temperature4,957[5] K
Metallicity [Fe/H]−0.164[7] dex
Age4.1[7] Gyr
B
Mass1.00[5] M☉
Radius1.1[8] R☉
Luminosity1.56[8] L☉
Surface gravity (log g)4.36[5] cgs
Temperature6,146[5] K
Metallicity [Fe/H]−0.26[5] dex
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
A
B

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.

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.[9]

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.[4] The A star that seems the brighter is over twice as far as B.[10] Parallax measurements from the Gaia satellite show the two stars, HD 238107 and HD 238108, are at distances of 311 ± 1 parsec (1,013 ± 4 light-years) and 144.2 ± 0.3 parsecs (470 ± 1 light-year) respectively. HD 238108 is itself a genuine binary star, with an 18th magnitude white dwarf companion 5 arcseconds away and a parallax distance of 146.8 ± 2.3 parsecs (479 ± 8 light-years).

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