Ch 31 Flashcards
Variable star
Stars in the giant branch of the h-r diagram. They pulsate in brightness because their outer layers expand and contract
RR Lyrae variable
A variable star that has a period of pulsation between 1.5h and 1 day. Has about the same brightness all the time
Cepheid variable
Variable star with a pulsation period between 1 and 100 days.
Halo
A spherical region in a galaxy where globular clusters are found
Spiral density wave
Alternating dense and less-dense areas that are frozen in place and rotate as a rigid pattern
Supercluster
A large cluster of galaxy clusters
Hubble constant
Represents the slope of a moving Galaxy
Radio Galaxy
A galaxy that emits as much or more radio energy as they do light. Often large and elliptical
Active galactic nuclei
Highly energetic objects in galaxies are located here
Quasar
Starlike object with emission lines in its spectra
Cosmology
The study of the universe, it’s current nature, and it’s orgin
Big Bang theory
The theory that the universe began as a point and has been expanding ever since
Steady state theory
Theory that the universe looks the same on large scales to all observers and it’s always been that way!!!
Cosmic background radiation
Weak radiation that appeared to come from all direction in space
Inflationary universe model
The theory that the universe began as a fluctuation in a vacuum and expanded very rapidly for a fraction of a second
