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# HW3 - Astronomy 1F03 Problem Set 3 Friday Nov 12th 2010...

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Astronomy 1F03 Problem Set 3 Friday Nov 12th, 2010 Please write your answers on a separate sheet and show your working. 1. a) The solar wind carries mass away from the Sun at a rate of about 2 × 10 9 kg/s. Determine how long it would take the Sun to lose all its mass at this rate. b) For comparison, calculate the rate at which the Sun is losing mass due to nuclear fusion. Fusion directly powers the luminosity of the Sun so you can use Einstein’s relation, E = mc 2 , to convert the luminosity into a mass loss rate. 2. Stars spend most of their lives on the main sequence and burn an appreciable fraction of their total hydrogen to helium in this period. In the following assume that stars spend their whole lives on the main sequence burning at a fixed luminosity and that all stars burn a fixed fraction of their total mass doing so. The Sun’s lifetime is about 10 billion years. Use this to estimate the lifetime of: a) A 0.25 solar mass, 0.01 solar luminosity red dwarf star.
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