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Name Block Stars Chapter 30 Pages 775- Star • A ball of gases that gives off a tremendous amount of ___________________________ ___________________________ • Notice that I did not say __________ • Stars emit all ______________________ of the EM spectrum Analyzing Starlight • • • Astronomers analyze stars by looking at the light they emit • Stars produce a display of colors and lines called a _________________ They use a ____________________________________ A spectrograph _______________ light into different colors or wavelengths Three types of spectra • ____________________________ or bright line • _____________________________or dark line—dark line shows composition and temperature • _____________________________ Star classification • If we look at a star with a spectroscope we see ______________lines called absorption spectra • These lines indicate the stars ______________________ _____________________________ The most common element in stars is __________________________________ Each chemical element has a characteristic spectra in a given range of temperatures The colors and lines indicate the ___________________that make up a star Name Block Color and Stars Think of a candle • Hottest part is ________________ • Red is the cool part at the top Apparent Motion of Stars • Time lapse photography show a circular pattern revolving around the star ______________________________ • We know Polaris as the North Star • It is located directly above the North Pole so as the Earth spins the stars appear to move Doppler Effect The apparent shift in the wavelength of light emitted by a light source moving ____________ or ________________ from a viewer Which way is the color shifted if the object is moving toward the viewer? Which way is the color shifted if the object is moving away from the viewer? Which color shift do we observe? Parallax The apparent shift in a stars location when viewed from different locations in orbit The _________________ the star is, the __________________ it appears to move Absolute vs. Apparent Magnitude • Absolute—how bright a star _______________________is • Apparent—how bright it __________________________from Earth Name Block Stellar Evolution Section 2 Page 781 The Hertzsprung Russell diagram –HR Diagram – 90% of stars are found on a diagonal line called the __________ _____________ – Hotter on the left cooler on the right – Brighter at top dimmer at bottom Groups of Stars • ________ ____________—diagonal line • Red Giants– _________ and __________ • Supergiants—brighter and cooler • White Dwarfs—___________ and hot Spectral Class • OBAFGKM • Oh Be A Fine Girl Kiss Me Birth of Stars • Nebula—interstellar clouds of _____________and ___________________ • • Drawn together by gravitational attraction called accretion • This huge ball of gas is called a ___________________________ Begins to ________________ as it condenses Birth of a star • • This ball continues to be drawn together by gravitational attraction • • This produces a huge amount of radiant and thermal energy When temperatures inside reach about _________________ Kelvins nuclear ________________________begins ___________________ of nuclear fuel marks the change from protostar to star Main sequence star • Most of a star’s life is spent as a _____________ ___________________ star • Its size, temperature, and color are relatively ________________________ • During this time it burns up its supply of _____________________ Name Block • What happens next depends on the star’s __________________ • When the sun has burned all its _______________, the helium core will ____________________ because of gravity • The rise in temperature will ignite the _____________ in the core and the core expands to become a _________ ____________________ • Our sun will reach this stage in about ____ ________________ years A Red Giant you know—_____________________________ The Fate of Stars differs according to their ____________________ (Low mass stars) • Small stars will shrink and throw off the outer layers in rings becoming a __________________________ _________________________ • The shrunken core that remains is a ___________________ _________________ – There is no nuclear fusion, it is only _______________________ hot – If it is a binary star it may form a nova, or, • When the core cools it becomes a ___________________ dwarf Medium Mass stars—like the sun ? Become RED GIANTS • Starts to burn helium-contracts because of gravity • This raises the temperature and the star expands • Our sun will reach this stage about ____________________ years from now White Dwarf • • • • • What remains after the star swells and ejects the outer layers • A cold, dark lump of matter that remains when a star has burned out and cooled off What remains no longer burns _________________ It slowly cools It is now a stellar remnant It can change color as it cools Black Dwarf Life cycle of a low mass star 1. Protostar-formed from nebula 2. Main sequence 3. Red Giant 4. Planetary nebula 5. White dwarf 6. Black Dwarf Name Block High mass stars have a different fate—they burn faster and • After the main sequence, stars with a mass much greater than the sun can burn and create larger and larger elements • When it gets to iron, it takes too much energy to create other elements so it collapses • This causes a ___________________, this is when heavier elements are made • Generate the elements of life • After a supernova a high mass star may become a • _______________________ star • The inner part implodes to form a super dense neutron star-- protons and electrons have fused to form neutrons • Or, if it is VERY massive it may form a ______________ ______________ Life Cycle of a High Mass Star • • • • • Protostar Main sequence Red giant or red supergiant Supernova Neutron star or black hole Black Holes Singularity—density is infinite Event horizon—_______________ ______ _______ _____________________ Answer these questions Revisit the HR diagram • Where are stars most of their lives? • Where are they when they begin to die? • What are they after they use up their fuel? How is the Life cycle of a high mass different????