ASTR 123, Robert L Zimmerman

Assignment #4: Chapter 24 Galaxies

Assigned Oct 27, 2009---------Due Nov 3, 2009

      You are asked to return various images and answer a few questions. You MUST place all images in a word processor. Under each image you must include a brief description. The description must be in your own words. 

                     Questions

1.  Draw a diagram of the Seyfert light curve (Fig 24.22). How does this diagram support the conclusion that Seyferts and Quasars emit their energies from regions that are smaller than one light-year? Circle this evidence on your drawing.

2. The two kinds of radiation emitted by a galaxy are plotted in Fig 24.35a. Describe the origin and characteristics of these two kinds of radiations.

3. Consider the comments in MORE PRECISELY 24-1 (Page 666) and answer the following questions

Distance to a galaxy is not very well defined so astronomers prefer to use look-back time.

a. Use the analogue of an? ant on a balloon to explain why distance is not well defined.

b What is the meaning of look back time?

c, Make a table of the look-back time and the time after the big bang for the following redshift z: Infinity, 10, 6, 2, and 1.  (The time after the big bang is defined to be the age of the universe minus the look-back time.} 

                       Images

4.  Carl Seyfert in the 1940s studied a class of galaxies that showed very bright cores. The nuclei varied in brightness on time scales of months. The spectra of these nuclei indicated enormous gaseous masses in rapid motion. These galaxies are called Seyfert galaxies (for their discoverer, Karl Seyfert). Return a picture of a Seyfert galaxy and a brief description found at

http://antwrp.gsfc.nasa.gov/apod/ap030726.html

5. Return an image of a double-lobe radio galaxy with a brief description found at

http://antwrp.gsfc.nasa.gov/apod/ap020226.html

Explain how core and lobe radio galaxies are related to each other.

6. Quasars (Quasi-stellar objects) lie near the edge of the observable Universe.  Return an image of a quasar with a brief explanation The URL is

http://antwrp.gsfc.nasa.gov/apod/ap000419.html

Use table 24.2 in your book to find the look-back time and the time after the big bang when the light was emitted. You will have to interpolate the numbers in the table to get an answer.