Jump to content


  • entries
  • comments
  • views

M 39 - A View from the City




M 39

M 39 is a rather unassuming open cluster about 101 thousand lights years away and estimated to be about 9 light years across. The vast majority of brighter stars are Type A, Dwarf stars, something similar to Sirius, in their main sequence stage (burning hydrogen at their cores), whilst the brightest star is a Type B with a magnitude of about 6. This understanding has lead to an age estimate for M 39 of about 240 to 280 million years; a long time, but as things go in the universe, M 39 is almost a baby, especially if you start comparing it with globular clustsers.

M 39 is one of the closest and smallest Messier clusters which helps explain its rather loose and angular visual appearance and even in a small aperture viewfinder, it is obvious that it is composed of stars, making it a wonder why Messier placed M 39 in his list of pseudo-comets in 1764. Other astronomers have been equally less-impressed. Herschel noted that it was 'coarsely scattered', Rosse of 'little concentration' and Smyth observed that it was a 'little splashy'.

City Observations

It is said that M 39 can be seen with the naked eye from a sufficiently dark site, appearing as a brighter spot within the rich star field of the Milky Way but in the city it is invisible and with no clear, nearby stars to guide you, it can be quite a challenge to find. Nevertheless, contrary to Herschel et al, I think it is well worth the effort.

In the viewfinder, M 39 looks like a triangle filled-in and surrounded by a relatively rich field of sparklers, making it a perfect observation for owners of low f/ratio scopes or low magnification eyepieces of about 32mm. I have no idea what stars should be included in the cluster, nor, let it be said, whether the sketch I have included is M 39 or one of the other rich clusters found in and around Cygnus. I have read that about 20% of the stars brighter than 10th magnitude do not even belong to the cluster, so probably what I have included in the sketch will be a tad misleading. If anyone could guide me here, I would be most grateful.

A useful tip for this given cluster is to sit with her for a while and let the different star colours become evermore apparent. I have tried to include the differing colours seen, but obviously this will be quite a subjective experience.

  • Like 2


Recommended Comments

is that a picture you took mate of the cluster? if so its awsome! im still to find my first messier :(

edit, oh hey qualia!! did not realise it was you lol :D :D :D

  • Like 1
Link to comment

Thank you for your kind words, TingTing. It's a sketch I made at the eyepiece; pencil in hand, bike torch gritted between my teeth, and other hand keeping the scope aligned as the stars drift away to the west. Quite a fun game, but I like it. Later I scan it into the computer, and make a few touches with Paint.Net a free software program.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.