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Download The Sun and Other Stars - Tuslaw Local School District
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The Sun and Other Stars Our Star the Sun • • • • • • • Center of the Solar System Our only source of - light, heat, energy An average star in size, mass, density, temperature Diameter = 864,000 mi. Volume = 1.3 million x earth’s Mass = 332,000 x earth’s *sun contains 99.86% of the mass of the Solar System The explosion of a 10 megaton bomb converts 1 lb. of matter into energy. The sun converts about 5 million tons of matter into energy each second. 2 Theories of Solar Heat Production 1. Fusion - a thermonuclear reaction • H + H = He + energy 2. Gravitational collapse - the sun is shrinking Other Stars • Electromagnetic spectrum - energy travels through space in the form of waves at a speed of 186,000mps • Wavelength - the distance from the crest of a wave to the crest of the next wave • Visible light has a wavelength < 1/1,000,000 m Telescopes • Optical - collects visible light 1. refracting - uses convex lenses to collect and focus light 2. Reflecting - uses a mirror to collect light *the bigger the diameter the more light gathering capability • Radio telescopes - used to detect radio waves rather than visible light Satellites - orbit the earth above the atmosphere Spectrographs - breaks light into color; collects info about stars - chemical composition and temperature Classifying Stars • Stars are classified according to size, temperature, brightness • Size - range from < 8000 mi. in diameter to > 2300 x’s the diameter of the sun • Color blue - white = hottest, yellow = average red = coldest brightness • Apparent brightness - as seen from earth • Absolute magnitude - the brightness a star would have if it were a standard distance from earth Hertzsprung - Russell Diagram ( HR Diagram ) • Shows the relationship between surface temperature and brightness The Theory of Stellar Evolution • Birth - a star is born out of a nebula - a large cloud of interstellar gas and dust The cloud condenses, due to gravity, and produces a protostar ( the earliest stage in a star’s life) and becomes hot enough for fusion to start Life of a star • How long a star lives depends on its mass *small mass stars use up their fuel more slowly than large mass stars, so they have much longer lives • Medium mass stars like the sun live about 10 by • Small mass stars may live 200 by • A large mass star 15 x’s as massive as the sun may live only about 10 my Death of a star • When a star begins to run out of fuel * center of the star shrinks * outer part expands • All main sequence stars eventually become red giants or supergiants • What happens next depends on the mass of the star * small & medium mass stars produce a white dwarf White dwarfs are about the size of the earth but have the mass of the sun! • A dying giant or supergiant can suddenly explode creating a supernova • The material expands into space creating a nebula • The material left behind forms a neutron star which are smaller and denser than white dwarfs ( 3 x’s mass of the sun, 20 km in diameter ) • Black holes - stars that are > 40 x’s the mass of the sun become black holes when they die * 5 x’s the mass of the sun, 30 km in diameter * the gravity is so strong nothing can escape including light! Pulsar - a neutron star that produces radio waves Quasar - a distant galaxy with a black hole at its center Distances to Stars • Light year - the distance light travels in 1 year - light travels at a speed of 186,000 mps (300,000km/s) - light travels about 6 trillion miles in 1 year - ( 9.5 million million kilometers) Parallax - the apparent motion of an object when viewed from 2 different points in space; can only measure distances to nearby stars Star Systems • More than half of all stars are members of groups of 2 or more stars called star systems • Binary stars - star systems w/ 2 stars • Triple stars - 3 stars Galaxies ( “Island Universe”) • Contain single, double, triple stars, star systems, lots of gas and dust between stars • Milky Way - the name of our galaxy • Classified into 3 main categories spiral elliptical irregular Big Bang - theory of the universe formation 10 to 15 bya Red shift - evidence of an expanding universe