# PHSC108_Hmwk4.pdf - PHSC 10800: Earth as a Planet Homework...

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PHSC 10800: Earth as a PlanetHomework #4Show all work for full credit—cite sources if you look anything up.Assigned: October 24, 2018Due for Full Credit: November 5, 20181)The Sun’s Energy Budget (25 pts)To first order, the Sun is powered by burning Hydrogen into Helium in nuclear reactionsthat occur near the center of the star.It takes 4 hydrogen nuclei to produce 1 Heliumnuclei in the interior of the Sun.The mass of one Hydrogen nucleus is 1.68588x10-27kgand the mass of a Helium nucleus is 6.69475x10-27kg.a)How much energy is released each time a Helium nuclei is produced?Use the netreaction that 4H -> He + Energy.Remember this comes from Einstein’s equationE=mc2.b)Given the temperature of the Sun is T⦿=5800 K, how much energy is being emittedfrom the Sun per second?That is, what is itsLuminosity?c)Given your answer in (a) How many Helium atoms must be created per second toprovide the energy that is emitted from the Sun every second?d)Assume the Sun is currently made completely of Hydrogen atoms, but only the innerregion, approximately 10% of its mass, has the conditions where nuclear fusion istaking place.If it is burning Hydrogen at the rate you calculated in (c), how longwould it take to burn through its fuel (that is, consume 10% of the total hydrogen)?

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