16. Characteristics of Stars Size: anywhere from 20km to 1 trillion km in diameter Mass: the amount of matter Color: stars can be red, blue, white, orange or yellow Composition: contain different elements determined using spectra
17. Characteristics of Stars Temperature: Blue is the hottest (35000 ° C) Red is the coolest (3000 ° C) Yellow (our sun) (5500°C)
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19. 0 -10 -20 -30 10 20 30 Magnitudes Dimmer Brighter Our Sun Sirius Brightest in the sky from Earth Polaris/North Star -26.5 -2 3 6 We can not see dimmer than +6 with naked eye
20. Star 1 High luminosity Far from earth = lower apparent magnitude Star 2 Low luminosity Close to earth = higher apparent magnitude Apparent Magnitude v. Luminosity
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22. Kinds of Stars super giants- largest of all stars, very luminous red giants- cooler, large, very luminous dwarf stars- less luminous, red, orange or yellow white dwarf- very faint, small and dense
23. Variable Stars- vary in brightness over regular periods or cycles 2 types: A. pulsating change in brightness as they contract (brighter) Or expand (dimmer) Example: cepheid - yellow supergiant
24. B. nonpulsating Eclipsing Binary 2 stars of unequal brightness that revolve around each other brightness depends on which one is in front of the other
25. Pulsars star that releases light and radio waves in pulses may be the neutron star formed in a supernova it looks like it pulses because it is rotating , like a searchlight
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30. Life Stages of Stars With Solar Masses less than 8 Solar Masses
31. Main Sequence Star (Our Sun) — >90% of all stars >The star is stable >Burns Hydrogen gas to Helium in its core through nuclear fusion > The energy released causes the star to shine. >Stars spend about 90% of their active lifetime as main sequence stars. Red Giant — >The star begins to run out of fuel and the core begins to shrink >Helium turns into Carbon >Rapid burning of helium causes outer layer to puff out, cooling the star >The star turns red
32. Planetary Nebula — >Outer layers are ejected as core continues to shrink >Shell of hot gas >Core is exposed White Dwarf — >Low mass core continues to shrink creating a white dwarf >Surrounded by the Planetary Nebula
