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Astronomical observations of our Milky Way galaxy indicate
Chapter 6, Problem 47(choose chapter or problem)
Problem 47PE
Astronomical observations of our Milky Way galaxy indicate that it has a mass of about 8.0×1011 solar masses. A star orbiting on the galaxy’s periphery is about 6.0×104 light years from its center. (a) What should the orbital period of that star be? (b) If its period is 6.0×107 instead, what is the mass of the galaxy? Such calculations are used to imply the existence of “dark matter” in the universe and have indicated, for example, the existence of very massive black holes at the centers of some galaxies.
Questions & Answers
QUESTION:
Problem 47PE
Astronomical observations of our Milky Way galaxy indicate that it has a mass of about 8.0×1011 solar masses. A star orbiting on the galaxy’s periphery is about 6.0×104 light years from its center. (a) What should the orbital period of that star be? (b) If its period is 6.0×107 instead, what is the mass of the galaxy? Such calculations are used to imply the existence of “dark matter” in the universe and have indicated, for example, the existence of very massive black holes at the centers of some galaxies.
ANSWER:
Solution 47PE
Step 1 of 6
The mass of the milky way galaxy is given to be times solar mass, using the given distance
of star from the center we need to calculate the orbital period
of the star. Also, in the part(b) we need to calculate the mass of the galaxy
for the given value to time period of star as
. By using the value of distance traveled by the light in 1 year as
.