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The sun- MIdterm 3.docx

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Department
Astronomy
Course
CAS AS 101
Professor
Paul Withers
Semester
Fall

Description
AS 101: THE SUN 1 .Why does the sun shine? The Sun: • 100x the radius of Earth • 300,000x the mass of Earth • Luminosity of 4 x 10 W • 70 % Hydrogen, 28% helium • Surface = 5800k • Core = 15 million K • Pressure is 200 billion times our atmospheric pressure Nuclear Reactions: • Radioactive Decay  o Potassium­40 (19p, 21n)  ▯Argon­40 (18p,22n) • Nuclear Fission o Uranium­236  ▯Kyrpton­92 and Barium­141 • Nuclear Fusion o Unlike Radioactive decay and nuclear fission, nuclear fusion wont decay  from just lying around  MASS MATH – VIA BB • Mass energy – Radioactive Heat Energy  Burning Hydrogen: * 600 billion tons of hydrogen turns in 596 billion tons of helium each second  • Why do they stick together and not repel? • How come this can only take place in the center of the sun and not in Jupiter’s  atmosphere? AS 101: THE SUN 2 Important Factors: • What is the Sun like? o Temperature, Pressure, composition and interior structure o Why does the sun shine?  What is needed for nuclear fusion to occur?  What does nuclear fusion do in the Sun? o How does fusion work? Discuss: ­ Why do protons stick together to produce energy in the sun? o As protons get closer, they repel more. o Strong nuclear force – allows them to attract (only work w/ short distances) o Nuclei must be 5 x 10 m apart to attract. o Protons need to move at roughly 5 x 10 in order for them to attract. ­ Why do we need high temps and high protons for fusion to occur? o 1 million kelvin isn’t even hot enough o 10 million kelvin (high enough temp to make things stick) Extreme Conditions Needed:
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