|M56 (NGC 6779)
|19h 16m 26s
|+30° 11′ 01″
Lyra’s most famous Messier object, indeed, one of the most famous of them all, is the Ring Nebula, M57. You can find our guide to seeing that here.
This cluster, which looks a little like a comet at low power, is an entirely different proposition to the planetary nebula of M57. It’s a grouping of stars with a mass of 230,000 suns, that lies about 33,000 light-years away from our little planet. It was discovered in 1779 by Messier himself but it wasn’t until five years later that William Herschel first resolved stars within it.
It orbits our home galaxy, the Milky Way, in the wrong direction, suggesting it is the result of a long-past collision and merger with a dwarf galaxy. What we see with our telescopes is the remains of the galactic core, formed 13.7 billion years ago and spanning 84 light-years of space. Its age makes M56 one of the oldest known globular clusters.
This cluster is approaching us at 110 miles per second (177 km per second). The brightest stars in its control shine at magnitude 13 and so can’t be fully resolved in a telescope smaller than about eight inches. However, the whole cluster is bright enough to impress in much smaller models.
The first sky chart, from SkySafari 6, shows just how high M56 gets in our late summer sky. This is the view at 9pm in the middle of September and you can see that it’s only a few degrees away from being directly overhead, a spot marked by the green ‘zenith’ cross. Stars in this first chart are shown to magnitude 5.0.
Stars in the next chart are shown to magnitude 6.0.
The unmistakable shape of Lyra is easy to pick out overhead, marked as it is by the second-brightest star in the night sky, Vega. To the left of Lyra is the great constellation of Cygnus the swan, with is readily identified cross shape soaring overhead.
To find M56, locate the stars Albireo in Cygnus and Sulafat in Lyra (both marked on the sky map below) and connect them with an imaginary line, shown as a dashed orange line below. Almost halfway along that line, but slightly closer to Albireo, is where M56 can be found.
The third and final chart shows stars to magnitude 9.0. Follow the line from Albireo to Sulafat to locate the cluster.
Now you’ve found the cluster, what should you expect to see?
The following views will help you find M56 in different telescope types by presenting the images as your telescope will show them. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Black stars on a white background is often easier to use at the telescope. Each image can be clicked on for a full-screen version. Stars are shown to magnitude 10.0.
Upright View – This is what your eyes see unaided and through a reflex or red-dot finderscope
Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal
Mirrored View – Refractors and Cassegrain models with a star diagonal show this view
Even though its official size is over eight arcminutes, we can’t see that much of it from our backyards. In a smaller telescope, you’ll see M56 as a comet-like blur covering maybe three arcminutes.
This small, hazy patch of sky has a noticeably brighter center, but not as bright as other globulars we’ve seen. On its western side is a resolved star shining at magnitude 10, this is not part of the cluster, rather than one lying in our line of sight.
Slightly larger telescopes reveal the mottled nature of the core and will resolve stars further away from it, within the cluster’s halo. See what magnification you can use to tease out resolved stars.
A decent magnification on a large telescope resolves many more of the core’s delicate stars, the brightest of which shine at about thirteenth magnitude.
Each of the star maps above is reproduced as a pdf below. Each star map has a number in [square brackets] beneath it which corresponds to the file number below. If you want image [M56-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.