Lecture-9 - 10/26/11 Physics 20 Lecture 9 1 Lecture # 9:...

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Unformatted text preview: 10/26/11 Physics 20 Lecture 9 1 Lecture # 9: The Sun and our Planetary System The Solar System The Sun Structure of the Sun Sources of energy in the Sun Solar flare, solar wind, sun spots The planets 10/26/11 Physics 20 Lecture 9 2 The Planetary System 10/26/11 Physics 20 Lecture 9 3 10/26/11 Physics 20 Lecture 9 4 Energy From The Sun Solar Constant : 1400 Watts per Square Meter at Earth Surface area of sphere with radius of 1 AU (1.5x10 11 m) is 4 (1.5x10 11 ) 2 = 2.8x10 23 m 2 Total Energy emitted from Sun each second is called Solar Luminosity (L ) L = 3.85 x 10 26 Watts from Blackbody Radiation from Suns surface at T = 5780 K 1 Watt (power) = 1 Joule (energy) per second 10/26/11 Physics 20 Lecture 9 5 Source of Suns Energy ? Chemical--last for only few thousand years Meteor /Comet Impact--1 solar mass falls into Sun every 100 years--see change in Earths year as mass of Sun increased (2 s per year) Gravitational Contraction--gravitational potential energy converted to heat as Sun shrinks in size--40 m per year--enough for ~25 million years. Late 19th Century: geological, physical and evolutionary evidence pointed to Earths age in the billions of years. Nuclear potential energy: ~10 billion years (E = mc 2 ) 10/26/11 Physics 20 Lecture 9 6 Nuclear Fusion in Suns Core 1905-Albert Einsteins Theory of Special Relativity- relationship between mass and energy E = mc 2 1939-Hans Bethe (Nobel Prize): Nuclear Fusion and the Proton-Proton Cycle 4 1 H 1 1 2 He 4 + photons ( energy ) The mass loss from converting 4 protons (hydrogen) to a single helium nucleus is 0.7% (.007) of the original proton mass 10/26/11 Physics 20 Lecture 9 7 Proton-Proton Cycle Requires temperatures greater that 10 million degrees (K) to overcome charge repulsion 10/26/11 Physics 20 Lecture 9...
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This note was uploaded on 11/17/2011 for the course PHYSICS 20 taught by Professor Mubarek during the Spring '11 term at UC Riverside.

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Lecture-9 - 10/26/11 Physics 20 Lecture 9 1 Lecture # 9:...

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