The Lifecycle of Stars

Measuring stars Constellations are groups of stars that make a picture: big dipper Orion

Measuring distance A Light year is the distance light travels in one Earth year It is a measure of distance NOT speed!

Measuring brightness Magnitude is the brightness Absolute magnitude is the actual brightness of a star Apparent magnitude is how bright a star appears from Earth Luminosity is the energy output from the surface of a star per second

All stars have nearly identical composition Their differences in appearance is a result of their differences in surface temperatures Blue 40,000K (~71,000oF) White 10,000K Yellow 7,000K Orange 5,000K Red 3,000K (~4,900oF)

Star size (mass) can also vary Our sun = 1 solar mass (2x1030kg) Giants = are 8-30 solar masses Super giants = 30-70 solar masses Also called “super massive”

H-R Diagram Plots data of mass, diameter, temperature, luminosity Y-axis plots absolute magnitude X-axis temperature (and spectral type) Main sequence—90% of all stars fall w/i this band of stars on the diagram These stars all have similar properties of structure and function

HR Diagram

Stellar Evolution Stars have a lifecycle Birth of the star is a nebula Maturity is main sequence Old age are red giants or super giants Death are white dwarf, neutron star, black hole

Star Formation All stars begin the same way but their evolution is determined by their mass

Black Hole Warping of space due to gravity