M 40 (Winnecke 4)

M 40 (Winnecke 4) is a double star in the constellation Ursa Major, magnitude 9.7.

Not a nebula or cluster but a pair of unrelated stars, Winnecke 4, which Messier logged while looking for a nebula reported in this area; it stays in the catalogue by tradition. Its components (magnitudes 9.7 and 10.2; spectral types G0 (yellow) and F8 (yellow-white)) lie 53.2″ apart at PA 76° (measured 2017).

When and where to see it

It is best placed in the evening sky around April, when it crosses the meridian at about 10 pm local time (around midnight in March). It can be seen from everywhere north of 32°S and never sets north of 32°N.

At its highest it stands 82° up from 50°N, 67° up from 35°N, 32° up from the equator, below the horizon from 35°S.

Facts

Type

Double star

Constellation

Ursa Major

Designations

Winnecke 4

Magnitude

9.7

Position

RA 12h 22.3m, Dec +58° 5′ (J2000)

Open AstroPilot to see when M 40 (Winnecke 4) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.