The night sky is full of objects to see and wonder at, and we astronomers know that. No matter how long you've been stargazing, there's always something new to point your telescope at.
However, any meaningful observation of the cluster requires a good knowledge of it.
This guide helps you with that. In it, you'll learn everything you need to know to plan your own session of viewing many of the galaxies in this group... and discover some little-known elements of it to share with your astronomy club.
So let's begin!
Virgo Cluster Basics
The Virgo Cluster is a conspicuous object in the night sky. It's also the farthest object from our galaxy which has a physical connection with us.
It is a gigantic cluster of galaxies found in the constellation of Virgo. Another such cluster is the Local Group, which our own Milky Way and the Andromeda Galaxy are part of.
Our Local Group and the Virgo Cluster are a part of an even bigger object - The Virgo Supercluster.
This enormous object is bound together by the collective gravity of the constituent galaxies and spans an unimaginable 110million light years of space.
To help get your head around such a phenomenal structure, below is a 3D map showing the various subclusters in the Virgo Supercluster:
If your mind is not blown yet, it will be when you learn that the Virgo Supercluster is just one of 10 million superclusters in the observable universe!
Let's drill back down to the more manageable Virgo Cluster.
Although it is vast, it is also a very long way from here - around 53million light years, in fact. So, in our sky, the entire cluster fits in an area about 8 to 10 degrees wide.
It consists of spiral, dwarf and giant elliptical galaxies arranged in three 'subclumps' or smaller clusters:
All three subclumps are slowly falling into each other under gravity and will eventually form one single cluster.
M49, M86 and M87 were first cataloged by Charles Messier (although he thought they were nebulae) along with 13 other galaxies. He made note of them in the 1770s and 1780s, so it's a safe bet that your telescope is better than his.
With that in mind, good seeing, a dark site, and a scope of around 6", it's not unreasonable to target seeing 20 or more of the galaxies in the Virgo Cluster.
With our target set, let's get into how we're going to achieve it. We'll begin with finding the Virgo Cluster in the night sky.
Ideal Equipment for Seeing the Virgo Cluster
The brightest element in the galaxy cluster is M49, with an apparent magnitude of 9.3. This is well beyond even the best eyesight and so you will need to make use of a good telescope for deep space objects to enjoy any of the galaxies in the cluster.
As this thread from Cloudy Nights reports, a 6" aperture and dark skies is enough to see the best of the Virgo Cluster. With an 8" scope at your disposal, the 30-or-so galaxies brighter than magnitude 12.0 are within reach.
You will get best results using an eyepiece with a wide field of view. Something like this Orion 20mm Plössl on Amazon has 52° apparent FOV and is a great price.
If you have more cash (this next one is 4x the price on Amazon of the Plössl) then Orion's 17mm Stratus eyepiece yields a 68° FOV and fits both 1.25" and 2" scopes.
Finally, for finding your way around, you can't go wrong with a red flashlight and Sky & Telescope's Pocket Sky Atlas. This has a dedicated page for the cluster with good - but not overwhelming - levels of detail.
How to Find the Virgo Cluster of Galaxies
Additionally, it will be useful to have Stellarium or Sky Safari 5, which the following screenshots come from. You can also use the essential Pocket Sky Atlas, which has a page dedicated to the Virgo Galaxy Cluster.
Let's begin. First, you'll need to spot the Virgo constellation. Leo will be right beside it.
Locate these three stars: Auva and Vindemiatrix in Virgo and Denebola in Leo (circled in red, below). These are the loose boundary for the Virgo Cluster of galaxies and make the perfect starting reference point.
Before we (finally) get into looking for individual galaxies, there is one other observing challenge you should know about.
Markarian's Chain is a line of 8 galaxies - all gravitationally associated with each other - that string out in an arc. See the image below and note it includes M84 and M86.
A wider field of view will show you many of them at once; using higher magnifying power when you have them in sight will enhance details.
Markarian's chain also contains the Eyes Galaxies. These are NGC 4435 and 4438. Together, they are bright, round galaxies named after two Greek words for 'eye': Oppa Virginis and Omma Virginis.
This small chain of eight galaxies is a nice challenge for an evening's viewing and rewards with a glow of satisfaction when you 'bag' all of them.
The eight galaxies of Markarian’s chain are included as a stand-alone observation list with our Sky Safari 5 Virgo Cluster list.
Seeing Individual Galaxies in The Cluster
Before you start looking for the galaxies themselves, remember two important things about seeing them:
- More light is better, so bigger telescope apertures give better results than smaller ones. An 8" aperture will yield superior sights to a 6".
- Galaxies are easier to find in a wider field of view. Start with lower magnification and only increase it once you've located the object you are looking for
With that said, let's dive into the galaxies themselves...
As mentioned earlier, there are 16 Messier objects - all galaxies - in the Virgo Cluster.
Whilst they are plentiful, and some are quite bright, don't underestimate the challenge of spotting individual objects.
The challenge in seeing them comes from the fact they are mostly faint and they are close to each other. Through the eyepiece, they are not much more than grey, fuzzy patches (although a decent telescope filter can improve detail).
There are three routes to seeing the best this cluster has to offer:
- Figure it out for yourself using a star atlas and Stellarium
- The the guide in Kenneth Glyn Jones' book Messiers, Nebulae and Star Clusters. It is part reproduced below and can be freely downloaded from SEDs
- Grab our pre-programed observation list for $1.99. It covers the brightest 30 galaxies in the Virgo Cluster and is compatible with Sky Safari 5.
Extract from SEDs Guide to Observing the Virgo Cluster
Click the picture below to get a larger version.
The Virgo Cluster of Galaxies is an area of our sky rich in relatively bright galaxies.
In this article we've shared with you how easy it is to find the area, how vast it is and the unimaginable distances involved.
We've also shared the most important factor for any backyard astronomer: how to see it!
If you want our Sky Safari 5 observation list for yourself (for only $1.99) click here. If you don't own Sky Safari 5 yet and would like to find out more, click the relevant link below:
- Star Hopping, by Robert Garfinkle (book)
- Concise Catalog of Deep Sky Objects, by Warren H. Finlay (book)