COSMOLOGY The study of the origin, structure, and future of the universe

Hubble Space Telescope Made studying the Universe easier.

Edwin Hubble 1920’s discovered that light from distant galaxies is being shifted to the red end of the spectrum. A shift in the spectrum towards the red side means an object is moving away. By examining the amount of red shift, he determined the speed at which the galaxies were moving away from Earth. He discovered that the most distant galaxies were moving away from Earth the fastest. He showed that the universe is expanding.

Redshift of Light from Distant Galaxies

The BIG BANG THEORY Billions of years ago, all the matter and energy in the universe was compressed into an extremely small volume. Approximately 14 billion years ago, an event (the Big Bang) sent all the matter and energy outwards in all directions. As the universe expanded, some of the matter gathered into clumps and formed galaxies. Today, the universe is still expanding.

Cosmic Background Radiation Discovered in 1965 by Bell Laboratories. Radio telescopes detect cosmic background radiation (low levels of energy). – Microwaves Astronomers believe that this energy is left over from the Big Bang.

Dark Matter Has gravity that can be detected Does not give of light Dark Energy Very little is known about it May act as a force that opposes gravity May be pushing galaxies apart. Due to this energy, the universe is not only expanding but the rate of expansion seems to be accelerating.

Globular Clusters Open Clusters Sometimes nebulae collapse to form groups of hundreds/thousands of stars, called clusters (all of the stars are roughly the same age). * Tens of thousands of stars * Spherical shape * Left over from galaxy formation (older) * Only hundreds of stars * Irregular shape (not spherical) * Still forming in galaxies (younger)

Galaxies A large scale group of stars, gas, and dust that is bound together by gravity. Milky way contains roughly 200 billion stars. Universe has hundreds of billions of galaxies.

Types of Galaxies Elliptical……Spiral…….Barred Spiral…..Irregular Spiral galaxies have a bulge at the center and they have spiral arms

Lenticular Galaxies Have a bulge at the center, but they do not have spiral arms

Milky Way Our galaxy Barred Spiral Billions of stars 225 million years for the sun to complete one orbit around center Part of the Local group A super massive blackhole is thought to exist at the center of the galaxy