Title: Week 7 Quiz
Course: ASTRON103: The Evolving Universe: Stars, Galaxies, and Cosmology (001) DHH SU18 > Section: Week 7

Q: Which type of galaxy is more red in color, a spiral or elliptical galaxy? Explain why.

Q: Using a value for Hubble's constant as 22 km/s per million light-years, what would be the recessional velocity (in km/s) of a galaxy that is 10^8 light-years away from Earth? Show your work.

Q: The brightest quasar in our sky is as bright as the Sun would be if viewed from a distance of 1300 light years away. This quasar, called 3C 273, is located at a distance of 2.4 billion light-years. Estimate the luminosity of this quasar in units of Solar Luminosity. Show your work.

Q: You try and measure a Hydrogen absorption line for a distant object. The absorption line has a rest wavelength of 486 nm. The measurement you make appears to be at a wavelength of 583 nm for the same absorption line for this distant object in km/s. Calculate the recessional velocity of this object. Show your work.

Q: Describe how distant, very young galaxies, are different from the nearby galaxies we see today.

Q: Suppose you are standing in the center of a large, densely populated city that is exactly circular, surrounded by a ring of suburbs with lower-density population, surrounded in turn by a ring of farmland. From this specific location, would you say the population distribution is isotropic? Homogeneous? Explain why / why not.

Q: If a black hole cannot allow anything to escape from it, including light, how can a quasar be associated with a supermassive black hole? What is the bright "stuff" we are actually seeing?

Q: One of the early hypotheses to explain the high redshifts of quasars was that these objects had been ejected at very high speeds from other galaxies. This idea was rejected, because no quasars with large blueshifts have been found. Explain why we would expect to see quasars with both blueshifted and redshifted lines if they were ejected from nearby galaxies.

Q: Suppose the stars in an elliptical galaxy all formed within a few million years shortly after the universe began. Suppose these stars have a range of masses, just as the stars in our own galaxy do. How would the color of the elliptical change over the next several billion years? Explain.

Q: The Milky Way shows evidence for having dark matter when you consider how its rotation speed does not decrease at large distances from the center of the Galaxy. Describe how observations of galaxy clusters also show evidence for the existence of dark matter.