Stars Stars color determine its temperature. Blue is hottest, red is coolest. Sun is yellow, average temperature. Stars made of mostly hydrogen and helium. Can also contain carbon, nitrogen, and oxygen.

Stars Continuous Spectrum Full range of all colors (rainbow) of visible light Emission Lines Specific color emitted by elements in a star Brightness Absolute magnitude is how bright a star would be if it was 32.6 light years from Earth. Apparent magnitude is how bright we see it when we look outside.

Stars Distance & motion of stars Hard to measure as they are so far away--measured in light years. Light-year = 9.46 trillion kilometers Parallax is a shift in position throughout the year that helps measure the distance. Closer the star is the more parallax it will show.

Life cycle of Large Stars Nebula—massive cloud of gas and dust Protostar--gravity pulls it into a sphere Main-sequence--Longest stage of life of our stars Supergiant--star expands outward and cools, contracts, then… Supernova—violent explosion expelling outer layers of lighter elements. What remains is… Neutron Star, Black Hole, Pulsar

Life cycle of Medium Stars Nebula—massive cloud of gas and dust Protostar--gravity pulls it into a sphere Main-sequence--Longest stage of life of our stars Redgiant--star expands outward and cools, contracts, then… White Dwarf—Small remnant of star with the mass of 1.44 solar masses or less. No more nuclear fusion. Black Dwarf—Cold, dead star

Life cycle of Small Stars Nebula—massive cloud of gas and dust Protostar--gravity pulls it into a sphere Main-sequence--Longest stage of life of our stars. May last for trillions of years White Dwarf—Exhausts al nuclear fusion, then… Black Dwarf--Cold, dead star

H-R Diagram H-R diagram shows stars relationship between their temperature and absolute magnitude. Shows the stars’ life cycles. Temperature on the bottom or x-axis. Absolute magnitude is on the left or y-axis.

Massive stars Massive stars are extremely hot so they have short life spans as they burn fuel quickly. Supernovas--Very large explosion that sends layers of star into outer space. Neutron stars--Small and extremely dense star composed of neutrons. Pulsars--A spinning neutron star that sends out beams of radiation into space. Black holes--Collapsed star that is very, very dense that light cannot escape if it comes close enough.

our Sun H-R Diagram

Supernova neutron star black hole pulsar