Astronomy Assignment - Dark Energy, Dark Matter and Inflation

1. Why do we need to have dark matter in our cosmology even though we've never directly detected dark matter?

2. How was dark energy "discovered"?

3. How can we rule out stellar remnants (ie black holes and pulsars) from being DM candidates?

4. What is the horizon problem and how does inflation solve it?

5. Explain how the "top-down" scenario for the formation of structure (e.g. galaxies, clusters of galaxies) in the Universe differs from the "bottom-up" scenario

6. Use Google or any basic astronomy 101 text to answer the following. Do your best to explain, I'm not asking for anything overly technical, just a basic description.

There are two main types of stellar explosion: type Ia supernova (or more generically, type I) and a core-collapsed (CC) supernova.

What kind of star(s) produces Ia and CC supernovae?

What is the average mass or mass range for each?

What causes the explosion for each supernova type?

Is there any part of the star left over after the explosion, if so what are they called?