B. How Galaxies Get Their Names
Some galaxies are given descriptive names (e.g. "Andromeda", "Whirlpool") if they are particularly distinctive in location or appearance. But most galaxies are known from their designation in a catalogue. One of the earliest catalogues of objects in the sky was made by Charles Messier. Messier was looking for comets in the 1700's, but kept finding objects that looked fuzzy, like comets, but didn't move. Eventually, he created a catalogue of these objects, listing their positions so he wouldn't be fooled again into thinking they were comets. Later, a number of them were identified as galaxies. Although he categorized many brilliant objects in the night sky, his cataloguing system was completed in a random manner. So M1 (the Crab Nebula in the constellation Taurus) is nowhere near M2 (a globular cluster in Aquarius).
As the capability of telescopes grew, larger catalogues were created. One of the oldest, but still widely used, is the A New General Catalogue of Nebulae and Star Clusters, or NGC for short, published by J. L. E. Dreyer in 1888. The NGC numbers objects from west to east across the sky, so that all objects in the same area of the sky have similar NGC numbers. (The Andromeda Galaxy is NGC 224, and the Whirlpool Galaxy is NGC 5194). Other catalogues have been created from specific ground based observatories (e.g. ESO, the European Southern Observatory, and the Uppsala General Catalogue (UGC) from the Palomar Observatory), orbiting observatories (e.g. IR, for the Infrared Astronomical Satellite), or for specific objects with certain properties (e.g. The Markarian catalogue lists galaxies with bright ultraviolet emission). The numbers following the letter designation may indicate either the order in the list or the location of the galaxy in the sky.
Recommended Activity: Identifying Unusual Galaxies