Messier 40, Winnecke 4

Messier 40
Messier 40: With five small galaxies: Section of the STScI Digitized Sky Survey [147]


Messier 40 is one of the few errors in the Messier catalog and is only listed here to complete the collection. On October 24, 1764, Charles Messier was looking for a «nebula over the ridge [of Ursa Major]» described by Hevelius, which he had mentioned in his 1660 work «Prodomus Astronimae». He wrote: «Two stars, very close together and very small, placed at the origin of the tail of the Big Dipper. It is difficult to tell them apart with an ordinary 6 foot telescope. The search is for the nebula that is located over the back of the Big Dipper, which was reported in the Book of the Star Figure of 1660.» [281] But there is no nebula here that Hevelius could have seen, but only two very close together 9th magnitude stars. They might not have been clearly seen with the telescope of the time under poor observation conditions and were mistaken for a nebula.

Physical Properties

M 40 is identical to the double star Winnecke 4, which was added in 1863 by the German astronomer Friedrich August Theodor Winnecke as the 4th object in his list. The two stars are about 50 arc seconds apart. Later measurements with the space probes Gaia and Hipparcos showed different parallaxes of the two stars HD 238107 and HD 238108, which makes it clear that they have nothing to do with each other and just happen to be close to each other from our perspective The star HD 238107 (west) is 317 pc (1034 light years) away and the star HD 238108 (east) is more than twice as close at 145 pc (437 light years). [4, 145]

Galaxies Nearby

The galaxies in the immediate vicinity with the size classes 12 to 15 are much too weak for Messier - let alone Hevelius - to see them.

«Catalogue of Principal Galaxies (PGC)», Paturel et al. 1989 [144]
NameRA [hms]Dec [dms]mTypeDim [']Btot [mag]HRV [km/s]PA [°]
NGC 428412 20 12.8+58 05 21S2.5 x 1.214.44215102
NGC 429012 20 48.3+58 05 31SBR2.2 x 1.612.8303590
NGC 433512 23 01.5+58 26 38E1.9 x 1.513.44595145
NGC 436412 24 02.0+58 23 06L M1.2 x 1.114.24496
NGC 436212 24 16.8+58 21 23S.7 x .315.3

Finder Chart

M 40 is located in the constellation Ursa Major above the upper left box star Megrez (δ Ursae Majoris), directly at 5.5 mag bright star 70 Ursae Majoris. If you don't just want to look at an optical double star, you can search for the five faint galaxies in the vicinity. The constellation is highest in the sky from December to June.

Chart Messier 40
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

400 mm aperture: The optical binary star Winnecke 4 is rather unimpressive. The galaxy NGC 4290 is distinctive and appears oval. The other galaxies in the same field of view only appeared as fuzzy patches, partly only via averted vision. — Taurus T400 f/4.5 Dobsonian, Bernd Nies, Glaubenberg Langis, February 28, 2022


4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
144Catalogue of Principal Galaxies (PGC); Paturel G., Fouque P., Bottinelli L., Gouguenheim L.; Astron. Astrophys. Suppl. Ser. 80, 299 (1989); (2021-02-18)
145SIMBAD astronomical database;
147Aladin Lite; (2020-12-23)
149SkySafari 6 Pro, Simulation Curriculum;
160The STScI Digitized Sky Survey;
281«Catalogue Nébuleuses et des Amas D'Étoiles» Observées à Paris, par M. Messier, à l'Observatoire de la Marine, hôtel de Clugni, rue des Mathurins. «Connoissance des temps ou connoissance des mouvements célestes, pour l'année bissextile 1784 » Page 227; (2021-02-21)