l18p - Today Announcements: The average on Exam 2 was...

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ISP209s7 Lecture 18 -1- Today • Announcements: – The average on Exam 2 was 32.7/40; outstanding – Exam #2 extra credit is due tomorrow March 19 at 8:00 am. – HW#8 will be due 26 March at 8:00am. – Submissions for the Spring Break Story Contest are due March 19. All voting will be anonymous. • The life of the stars • The Uncertainty Principle Revisited ISP209s7 Lecture 18 -2- Our Sun • A huge, hot ball of mostly hydrogen and helium (3% other stuff) • Power output (luminosity) 3.26E+26 W • It is 93 million miles from Earth. Intensity at the Earth is about 1000 W/m 2 . That is like 10 100 W light bulbs every square meter • The Sun is a complicated object ISP209s7 Lecture 18 -3- Blackbody Radiation All objects emit a spectrum of photons. A perfect black body has the spectrum shown at the left. The emission spectrum depends on temperature. The amount depends on size. K eV k kT E K m W AT L mean 5 4 2 8 4 10 617 . 8 ; 705 . 2 10 67 . 5 ; × = = × = = σ ISP209s7 Lecture 18 -4- Our Sun is a complex object Spicules Corona
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ISP209s7 Lecture 18 -5- A Stars Energy Source – nuclear fusion
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l18p - Today Announcements: The average on Exam 2 was...

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