Astronomy 123: Third Homework Assignment


  1. What is some of the evidence for the existence of substantial amounts of Dark Matter in the Universe?

  2. What is a WIMP and why is it thought to be a good candidate for Dark Matter?

  3. What is a gravitational lens? Find a Web picture that shows an image of a gravitational lens and report the address of the web page.

  4. Galaxies frequently run into each other and have a tidal interaction. You will use a computational engine to model two interacting galaxies to see if you can reproduce the observed morphology of two real systems.

    This applet is doing calculations in your browser concerning the gravitational interaction between galaxies. You can twiddle the dials with left or right mouse button to change orientations. You can change mass ratios and distances of closest approach (peri parameter). You can choose to have a big dark matter halo around the galaxies or not (that's the Big Halo box).

    Your mission is to see if you can produce a simulation that looks like the real system below which is loaded as a background image in the engine. When the colored dots more or less overlap with the image, you can consider that a reasonably good model.

    Record the parameters of that simulation and the time (in millions of years, its printed at the top of the applet) when the simulation sort of looks like the real system. An example of a "successful" simulation would look something like this:

    There are two systems to model: (note: to get the simulation to fire up the first time hit start,stop,reset, start. Just hitting start may not work).

    System Number 1

    System Number 2