The Properties of Galaxies | Shapes | Colors | Sizes
4. The Size of Galaxies
Galaxies exist on a different size scale than anything else that we have studied in the course thus far. We have been pulling back from our Solar System over the semester just like the Powers of Ten film that we saw the first week. Now that we have reached our study of galaxies we'd do well to understand just how big they are (even though they appear the same size as many of the nebulae that we looked at during the Properties of Stars lab).

Once the distance to a galaxy is known its actual size can be calculated from its apparent size in an image. This was first accomplished by Hubble when he used Cepheid variables to find the distances to galaxies. Use the distance to M100 that you found earlier.  Here you'll use the Virtual Observatory to measure the angular size of M100.  Its coordinates are RA 12 22 55, Dec +15 49 21.  Use 15' for the Required Field of View.  Be sure to use the red filter and GIF image format.

CLICK HERE for a refresher in calculating angular size and actual size.

You can now use your new knowledge of the sizes of galaxies to better understand our perspective on the universe, which we'll begin to look at next.