This cluster of stars, known as the Pleiades, or Seven Sisters, is among the nearest star clusters to our own planet: 440 light years away! Blue, bright, and young (approximately 100 million years old), the Pleiades are a common sight in the winter night sky in the Northern Hemisphere. But they make up only a tiny portion of the vast universe in which we live. In this chapter, you will read about the components of that universe, from stars and star systems to galaxies and black holes.
Courtesy of NASA, ESA, AURA/Caltech, Palomar Observatory. commons.wikimedia.org/wiki/File:Pleiades_large.jpg. Public Domain.