galaxy: A large collection of stars and
associated clouds of gas and dust.
Galaxies are categorized by their
shape. Any type of galaxy—spiral,
elliptical, or irregular—can have a bar
or conspicuous elongated band of
stars. These galaxies are called barred.
 elliptical galaxies lack structure;
consisting of billions of stars evenly
distributed around their centers, they
appear as fuzzy blobs. 
 spiral galaxies look like flattened
disks with sweeping arms of stars.
They can come in a multitude of
shapes and sizes and are classified
according to the compactness of their