Object: M45, The Pleiades, Melotte 22 Type: Open Cluster

Diameter in '
Number of stars
Brightest star (magnitude)
Distance in parsecs (3.26Ly)
: Taurus
: 03 47.0 / +24 07
: 120
: 1.5
: 100
: 3.0
: 125
Details sketch
Date / Time
Observing Location
Seeing / Transparency
Magnification / Field of View '
: 16/02/10 / 20:00
: Landgraaf
: 4 / 3
: Orion 8x42 binoculars
: n.v.t.
: 8 / 492 (8.2°)

Observing report
Visually, M45 is one of the most beautiful open clusters in the night sky. With the naked eye I can detect 6 stars tonight. Through the 8x42 binoculars the Pleiades are a rich cluster of 50+ stars that fill the centre of the field of view. My 8x42 binocular has a true field of view of 8.2°. Through these binoculars I see the Pleiades as a large, two-degree wide, open cluster with plenty of sky around it to frame it nicely. All the stars look more or less white. I do not detect any coloured stars. The eight brightest stars form a nice asterism, which reminds me of the big dipper in Ursa Major. There are several chains of stars, but the one running to the southeast is the most conspicuous. Between the chains I see dark lanes without stars. There are a few double stars visible. The most interesting lies at the empty centre of the dipper. I remember from an observing session a few years ago, (observing the Pleiades with a 15x80 binocular) that one of the components of this double showed a yellow - orange hue. This colour stays undetectable in the 8x42. I do not detect any nebulosity.
M45 is one of the closest open clusters to the sun. It lies at a distance of 125 parsecs. As far is I know, there are only three open clusters that lie closer to the sun than the Pleiades. The closest star cluster is Collinder 285, the Ursa Major moving group, which lies only 23 parsecs from the sun. Next on the list are the Hyades, which lie at a distance from 46 parsecs. The third closest group is Melotte 111, the Coma Bernice's star cluster, at a distance of 90 parsecs.

I personally find M45 one of the most beautiful clusters when observed with the naked eye or a pair of wide-angle binoculars. From my light polluted backyard I can only see 6 members of the Pleiades: Alcyone, Atlas, Electra, Maia, Merope and Taygeta.

As you can see in the list below, showing the brightest stars of the Pleiades, they are all late B type giants. The main sequence of the Pleiades runs from type B8 right down to K2 type stars. The stars later than K2 type are still above the main sequence. They are in the phase of initial gravitational contraction toward the main sequence.

When you move the mouse pointer over the sketch above, you can see the double star ADS2755 pointed out with the yellow arrow. This was the double where I could see colour in one of the components with my 15x80 binoculars a few years ago. The western component of this double looks definitely yellow-orange. This is a K2 star.
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