AST 301
Homework #4
Due Friday Feb. 21
1. The Sun radiates about 4x1026 Watts of power from its surface.
a) If the Sun generates the same amount of power by nuclear reactions that it radiates from its surface,
how many Joules of energy does it generate each second?
b) A typical photon radiated from the surface of the Sun has about 4x10-19 Joules of energy. About
how many photons are needed to make one Joule of energy?
c) About how many photons are radiated by the Sun each second?
d) For every four hydrogen atoms converted into one helium atom inside the Sun, two neutrinos
are created and about 4x10-12 Joules of energy is generated. How many helium atoms are made for
each Joule of energy generated?
e) About how many helium atoms are made inside of the Sun each second? About how many
neutrinos are created each second?
2. If you lie outside on a summer day, the power in the sunlight hitting you is about 1000 Watts.
a) Using the numbers given in question 1, about how many sunlight photons are hitting you each second?
b) How many helium atoms were made each second to generate the power hitting you?
c) How many neutrinos from the Sun pass through you each second?
d) Why haven't you noticed all of those neutrinos?
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