Winnecke 4

Database links to Winnecke 4 / Messier 40

Optical double star
Winnecke 4

2MASS image of the double star WNC 4 / M 40
Constellation	Big Bear
Position equinox : J2000.0
Right ascension	12h 22m 12.53s
declination	+ 58 ° 04 ′ 58.6 ″
Further data
distance	(480/1035 LJ )
history
discovery	Charles Messier
Date of discovery	1764
Catalog names
M 40, WNC 4
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Winnecke 4 (short: WNC 4 ) is an optical double star in the Great Bear , consisting of a star of magnitude +9.7 mag and a star of magnitude +10.1 mag. This double star, which can be resolved in a powerful binoculars , was discovered by Charles Messier in 1764 , mistakenly mistaken for a nebula and thus given the designation M40.
The angular distance between the two stars is approx. 50 arc seconds, the less bright one being at a position angle of 83 degrees with respect to the brighter one. The designation Winnecke 4 results from Winnecke's double star measurements .

particularities

Before the measurements of Gaia , all attempts to determine the movement and distance data exactly had failed; the distance was estimated to be 170 ± 70 pc. The gravitational coupling was questionable and therefore unclear whether the object is a real double star. Any period should have lasted at least 232,000 years and the distance would have been at least 5000 AU , which is why the coupling was always considered improbable.

Combined astrometric solutions from the Hipparcos and Gaia satellites give parallaxes that correspond to distance estimates of 350 ± 30 pc and 140 ± 5 pc, respectively. This means that Messier 40 is not a physical double star , but consists of two completely independent stars. With Gaia DR2 , the distance information has once again been made more precise with 317 ± 3 for HD 238107 resp. 146 ± 1 pc for HD 238108 .