Materials Required:
· Computer and internet access
· Calculator
· Ruler
· Pencils and pens, eraser
· Digital camera and/or scanner
· Print out Galaxy Image Prints document
Total Time Required: Approximately 2-3 Hours
Part 1. The Local Group
In Table 1, you will find a list of most of the galaxies in the Local Group. This group is made up of our own galaxy, the Milky Way, and its closest neighbors. (Note: 1 kpc = 1 kiloparsec = 1000 parsec; 1 parsec = 3.26 light years)
1. Using Table 1 above and noting the diameters of the galaxies, which five galaxies in the Local Group are the largest? In a few sentences, compare the sizes of the other galaxies in the Local Group to the two largest ones.

2. Which three galaxies have the largest angular size (not including the Milky Way)? These galaxies are the ones that look the largest in the sky. Explain how you get your answer.

3. By hand and with pencil, create a scale drawing of the Milky Way and the Large Magellanic Cloud, showing their relative sizes and the distance between them in kiloparsecs (the galaxies can be represented by circles). Write down the scale you use , and your calculations to find the scaled-down sizes and distance. (An example of a good scale to use would like something like: 5 mm = 10 kpc, also see this site Basic-Mathematics.com for more information on scaling.) You will photo your drawing and insert it into your lab report.

Figure 2. Local Supercluster Print

Local Supercluster Print

Image courtesy of Palomar Sky Survey Photographs

As you have already seen, galaxies can vary a lot in size. Now, we will look at how their shapes are different. Two basic types of galaxies are the spiral galaxies and the elliptical galaxies. Spiral galaxies have a disk-like structure,and a central bulge. Our own Milky Way is a spiral galaxy. Elliptical galaxies appear round, looking a lot like a football or an egg.

Examples of both types of galaxies can be found in the research-quality Palomar Sky Survey. Photographs, Figure 2, of the part of the sky that includes the center of the Local Supercluster. This cluster is in the direction of the constellation Virgo, so it is sometimes called the Virgo cluster. The Local Supercluster is 15 million parsecs away from the Local Group, and it contains thousands of galaxies.

4.Go to this site, ESO image , which is also an image of the Virgo Cluster that you can zoom in to better see some of the galaxies. Within this image locate:

· two elliptical galaxies with different ellipticities,

· a spiral galaxy seen face-on,

· and a spiral galaxy seen edge-on.

Make a diagram on a sheet of paper to show where these galaxies are on the picture, and try to sketch their appearances in a similar-sized box. Note: it is best to create a type of grid system and note if the galaxy is, for example, to right, middle, etc (Make sure to label each type of galaxy on your sketch. Photo and insert your signed and dated sketch into your lab report.)

Part 2. The Local Group.

Now that we have a handle on how to classify galaxies, we can take a look at how galaxies are grouped in the Universe. This may give us some clues as to how they form and take on so many different shapes.

Galaxies are found throughout the universe, from our next door neighbors — the Magellanic Clouds and Andromeda — all the way out to the edge of the visible universe 13 billion light years away. Nobody knows for sure, but it is estimated that there are 100 billion galaxies or more in the visible universe, and many more beyond that. Galaxies live in a variety of environments. Sometimes large numbers of them are packed close together in clusters, such as the Coma Cluster; sometimes they gather in smaller numbers called groups, like the Local Group that contains our Milky Way; and sometimes they are isolated far from one another in the field.

Clusters, groups, and some isolated galaxies can all be part of even larger structures called superclusters. At the largest scales in the visible universe, superclusters are gathered into filaments and walls surrounding vast voids, often described as resembling large soap bubbles. This structure often is referred to as the “cosmic web.”

The Coma Cluster, which is centered about 320 million light-years away, contains several thousand individual galaxies. The cluster has a roughly spherical shape and is about 20 million light-years across. (For comparison, the Milky Way is 100,000 light-years across). That many galaxies in a relatively small space makes the Coma Cluster one of the richest and densest galaxy clusters in our region of the universe. (download and print out the ‘Galaxy Image Prints’ for this part of the lab) On these pages you will be asked to count different types of galaxies.