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ASTR302 Homework #3
(due in class on Monday, February 18, 2008)
1)
Assume that the Sun’s current luminosity (3.86 x 10
26
W) has remained constant over the last
4.5 billion years.
Also, the current mass of the sun is 1.99 x10
30
kg.
a) Estimate how many kilograms of hydrogen the Sun has consumed over the past 4.6
billion years.
b) Estimate the amount of mass that the Sun has lost as a result.
c) What percentage of original mass
has the sun lost over its lifetime?
d) In fact, the Sun’s luminosity when it first formed was only about 70% of its present
value.
With this in mind, explain whether your answers above are an overestimate or an
underestimate.
2) Sunspots typically consist of two regions: an umbra (T ~ 4300K) surrounded by a penumbra
(T ~ 5000K).
The surface of the photosphere is ~ 5800K.
a)
Find the wavelength of maximum emission from the umbra.
b)
Find the wavelength of maximum emission from the penumbra.
c)
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This homework help was uploaded on 04/03/2008 for the course ASTRONOMY 302 taught by Professor Keller during the Winter '08 term at Cal Poly.
 Winter '08
 Keller

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