Deep sky challenge
Messier 13 isn’t the only stellar gathering to see in the early summer sky
As spring slides into summer, the brightness of the night sky makes observing deep-sky objects quite a challenge. The misty nebulae and smoky galaxies that fill our eyepieces on the long, frosty nights of darker seasons become washed out by the lingering twilight. Fortunately, there are plenty of other deep-sky objects to track down and observe, like globular clusters.
Globular clusters are enormous, spherical groups of tens or even hundreds of thousands of stars, but because they are so far away they only appear as small, round smudges in our telescopes. The most famous globular in the northern sky is Messier 13, the Hercules Globular Cluster. It’s surrounded by many others that are well worth an observer’s attention on a clear night at this time of year, but suffer from being in its shadow – if the beautiful Messier 92 was in another part of the sky it would be much more popular, but with Messier 13 just a short star hop away, it is overlooked.
Also visible at this time of year is Messier 57, the Ring Nebula. Although it’s brighter than many of the other objects on this month’s list, your challenge is to detect its subtle pastel colours and the faint star at its centre.
1 Messier 56
This fine, eighth-magnitude globular cluster is roughly spherical. In a high-power eyepiece you’ll see an attractive mix of faint blue and red stars, with a triangle of brighter stars embedded in its western edge.
3 Messier 92
This sixth-magnitude globular cluster is a very rich, condensed ball of blue-white stars. Almost perfectly symmetrical, it is a beautiful sight in any telescope, but is sadly overshadowed by the much larger and brighter Messier 13 nearby.
5 Hercules Globular Cluster (Messier 13)
The finest cluster in the northern sky, Messier 13 is a spectacular sight in a large telescope: a beautiful ball of glittering bluewhite stars with cobweb strands of fainter stars spraying away from its outer edges.
2 The Ring Nebula (Messier 57)
The most popular planetary nebula in the northern sky, you’ll need to be under a very dark sky and using a large telescope to see its blue and green colours and the faint star in its centre.
4 The Prize Comet Cluster (NGC 6229)
This little-known tenthmagnitude globular cluster is 99,000 light years away. High magnification is needed to reveal its condensed core of pollen-grain grey-blue stars surrounded by a cage of brighter yellow stars.
6 The Snowglobe Cluster (NGC 5466)
With no central condensation this small, tenth-magnitude object looks more like an open cluster than a globular. Looking at it under high power, you’ll be reminded of a miniature version of Messier 44, the Beehive Cluster.