ABSTRACT
The universe today is a far different place than it was 13.7 billion years ago. This chapter contains some of the strangest terms in all of astronomy—words like pulsar, quasar, black hole, magnetar, blazar, along with red giant, blue supergiant, and black dwarf. A stellar mass black hole is created when a massive star collapses at the end of its lifetime. Supermassive black holes, which weigh billions of times as much as the sun, are found in the centers of galaxies. A blue supergiant can have a lifetime of less than a million years, compared with our sun’s expected lifetime of about 10 billion years. Cepheid variable stars are like measuring sticks in astronomy, because astronomers can tell how far away a Cepheid variable star is from Earth based on its brightness and how quickly it goes through a bright and dim cycle.
