Assignment 9: Chapters 17 and 18 // Due 11/12 [1] (10 points) Short answer questions:
(a) Name a galaxy besides our own that can be seen with the naked eye?
(b) What do astronomers attribute the ring of the cartwheel galaxy to?
(c) About how many times more luminous are powerful quasars compared to the Sun?
(d) About how many times more luminous are powerful quasars compared to a galaxy like the MW? (Hint: The Milky Way (MW) shines with about 20 billion solar luminosities)
(e) Why were astronomers originally led to believe that the energy producing region of a quasar must be small?
(f) About how many solar masses is the Supermassive black hole in the giant elliptical galaxy M87 in the center of the Virgo Cluster of galaxies?
(g) Where are giant elliptical galaxies found.
(h) How did giant elliptical galaxies get so massive?
(i) Name two very reliable standard candles for determining distances to galaxies.
[2] (10 points) How can a collision between galaxies produce a starburst galaxy? (Explain thoroughly)
[3] (10 points) Discuss two observations that seem to indicate that clusters of galaxies are embedded in huge halos of dark matter. (be specific give details)
[4] (10 points) Explain how supernovae type la are utilized to measure Hubble’s constant? Why are measurements of the redshifts of the galaxies that host the Supernovae type la just as important? Think Hubble’s law. (Explain thoroughly)
[5] (10 points) Distant galaxies have a dominant recessional velocity dictated by the expansion of the universe. If Hubble’s constant is 71 (km/sec)/Mpc, how far away is a galaxy receding at 8.88 x 103 km/sec?
Hint: See Astronomer’s Toolbox 17-1 page 573.
Extra Points (8 points) Centaurus A lies at a distance of 4 Mpc from Earth. This galaxy has radio jets that span across the sky –from the end of one lobe to the end of the other lobe with an angular diameter equivalent of 28.5 full moon widths.
If the jets are equal in length how long is one of them in parsecs?
Hint: one full moon is .5 degrees in angular diameter. Once you get the angular length of the jets in degrees convert to radians and use the arclength formula s = r 19„d to find the length ‘s’ of both jets in Mpc. Then convert to find the length of one jet in parsecs. (Show all work)
