Astronomy Lecture Notes Feb. 5
Astronomy Lecture Notes Feb. 5
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This 2 page Class Notes was uploaded by Lindsay Notetaker on Friday February 6, 2015. The Class Notes belongs to a course at a university taught by a professor in Fall. Since its upload, it has received 67 views.
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Date Created: 02/06/15
The Sun Diameter 14 X 10A6 km 109 diameter of earth Mass 20 X 10A30 kg 332000 X mass of earth Surface temperature 5800 K Core temperature 15 X 10A6 K 15000000 K Solar Energy The Sun s spectrum is close to that of an idealized blackbody with a temperature of 5800 K Luminosity total energy output per second 39 X 10A26 jouless 39 X 10A26 Watts detonation of 100 billion 1megaton nuclear bombs per sec The Source of the Sun s Energy nuclear reactions occur in the core of the Sun The reaction is called the protonproton chain Hydrogen is converted to Helium Energy is generated by thermonuclear fusion The temperatures and pressures deep within the core of the Sun are so intense that hydrogen nuclei can combine fuse to produce helium nuclei Converting Hydrogen to Helium 4 H 9 He energy The particles are 0 Positrons e positively charged electrons antielectrons I Positrons instantly encounter electrons and they annihilate to create a gamma ray 0 Neutrinos v weakly interacting neutral particles that travel at nearly the speed of light and have nearly no mass 0 Gamma ray photons y energy 0 Deuterium HA2 an isotope of Hydrogen with 1 proton and 1 neutron o Helium3 HeA3 an isotope of Helium with 2 protons and 1 neutron The sum of all the masses created in this reaction is less than the mass of the particles that were used up Mass of 4 hydrogen nuclei 66943 X 10A27 kg Mass of 1 Helium4 nucleus 66466 X 10A27 kg The lost mass 07 has been converted to energy E mcquot2 This is the energy that powers the Sun and that eventually radiates out into space The protons overcome their mutual repulsive force bc the temperature in the core of the Sun is very high 15 million K o This means that they move very fast in an extremely dense environment 0 They overcome their mutual repulsion stick together and fuse The energy generated as gamma rays leaves the Sun as visible light but it takes a few hundred thousand years to make its way to the Sun s surface o This is bc it is absorbed and reemitted many times as it bounces off matter in the Sun s interior However neutrinos generated in the core travel cleanly through the Sun bc they have no charge and interact very weakly with matter 0 they leave near the speed of light and escape into space a few seconds after being created 10A38 neutrinos are created in the Sun each second Every second about 10Al4 neutrinos pass through each square meter of the Earth
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