(1) When did astronomers first begin to study the structure of our galaxy using radio telescopes? Research this topic on the web and write a one half page summary about the people and the observations that made the first radio maps of the Milky Way. Be careful to avoid plagiarism and reference your sources.
(2) Briefly summarize the Shapley-Curtis debate. Were there any definitive conclusions drawn from this debate?
(3) The force that keeps the Sun in orbit around the center of the Galaxy is the gravitation pull of all the matter interior to the Sun's orbit. We can estimate the total mass of all of this matter using a derivation of Newton's form of Kepler's third law:
M = rv2/G
The value for r is the distance of the Sun to the center of the galaxy,26,000 light years.
The value for v has been estimated to be 220 km/s.
The value for G is the gravitational constant you have used for other calculations in this class.
Using these values, calculate the estimated mass of all of the galaxy interior to the Sun's orbit.
Remember that you will have to convert r from light years to meters and convert v from km/s (kilometers per second) to m/s (meters per second).
(4) Astronomers have been able to calculate our Solar System's speed around the center of the Galaxy by looking at objects outside of our Galaxy. Using this value, you were able to calculate the mass of the galaxy within the Sun's orbit around the galactic center. Does this knowledge of the Sun's velocity in its orbit tell us anything about the mass of the galaxy outside the Sun's orbit? Explain your answer.
(5) When astronomers identify the location of black holes by observing orbiting companion stars, how do they know that these stars are not really orbiting pulsars or white dwarfs?
(6) Why did 19th century astronomers think that the "spiral nebulae" were part of our Milky Way galaxy?
(7) What is the Local Group of galaxies? What are some of the prominent galaxies in this group?
(8) Some galaxies in the Local Group exhibit blueshifted spectral lines. Why is this not a violation of Hubble's law?
(9) The galaxies with the least amount of gas and dust are:
(a) barred-spiral
(b) elliptical
(c) irregular
(d) spiral
(10) What type of galaxy do we usually find at the centers of galaxy clusters?
(a) barred spiral
(b) elliptical
(c) irregular
(d) spiral