M 29 - An Open Cluster

M 29 is an unassuming, rather lacklustre open cluster made up of about seven bright stars some 3,740 to 7,000 light years away in the constellation of Cygnus and anyone with a 4" telescope or larger may wonder how it was ever included in Messier's list of objects not to be confused with a comet. The answer can be found in Messier's own notes where he writes of the star grouping as "seen...in the form of a nebula", perhaps highlighting just how poor the optics and lenses were in Messier's own time.

I imagine M 29 would be a rather spectacular cluster if it weren't for a thick cloud of interstellar dust blocking and diminishing the star light by as much as 95%, meaning that many of the stars in the cluster are dimmed by as much as 5 magnitudes. The stars themselves are thought to be young, very hot, and luminous, indicating that the cluster's age is between 4 to 6 million years old. The four or five brightest stars are type B, blue supergiants each with a luminosity of about 160 thousand suns.

It is estimated that there are over 200 stars in the cluster but on an average seeeing night in the city (mag 3), you should be able to make out about a quarter of this number with ease.

Observation Notes and Sketch

The problem with sighting M 29 is twofold:

i) it is so unassuming, you're not too sure whether you've found a Messier object or just a rather pretty star pattern.

ii) this area of Cygnus has quite a rich field of stars due to being just outside the Milky Way. Thus it is quite tricky to know where the cluster begins and ends.

At about 40x the resolution of M 29 into individual stars is easily achieved. The seven of eight brighter stars have a block-box-trapezoibal appearance which does give M 29 a rather austere, mechanical like feel.

The sketch was made using relatively thick black paper, a white charcoal pencil to mark the stars and then touched up indoors with a tippex pen for the brighter stars. It was scanned into the computer and tidied just a little with the free software Paint.Net.