Stars, Galaxies, and the Universe

The Life Cycle of Stars First Stage ball of dust and gas pulled together by gravity nuclear fusion begins when star becomes denser (changing hydrogen to helium)

Main-Sequence Stars Giants and Supergiants 2nd stage longest stage creating energy through nuclear fusion 3rd stage red giant = large, reddish star late in life cycle expands and cools once hydrogen is all used up

White dwarfs Final stage small, hot dim star that is the leftover center of an old star

Supernova Neutron Star gigantic explosion massive star collapses and throws outer layers into space follows a supernova star that has collapsed under gravity to the point where all of the star’s particles are neutrons

Pulsar Black Hole spinning neutron star object so massive and dense even light cannot escape its gravity happens when center of collapsed star has a very high mass

Top – smaller star, like our sun Bottom - large star, like Betelgeuse

Galaxies

Formation of the Universe Cosmology Galaxy Movement study of origin, structure, and future of the universe scientists study movement of galaxies measurements show galaxies are moving apart Raisin Bread Model  As the universe expands, galaxies move further apart

Big Bang Theory universe began with a tremendous explosion about 13.7 billion years ago Radiation found coming from all direction in space left over from big bang

Structure of Universe Age of Universe every object is part of a larger system Ages of stars help calculate the age of the universe universe is at least as old as oldest star Distance between Earth and other galaxies rate expansion

A Forever Expanding Universe scientists predict if there was enough matter, gravity could eventually stop expansion and it would collapse to original state they do not believe there is enough, so they think it will expand forever (even after stars die and it becomes cold and dark)