CEN 511: Recent Discoveries in Astronomy

1. What is the difference between energy and power?
2. In one hour, how many kilowatt-hours (kwh) of energy does the Sun radiate?
   1. This amount of energy is equivalent to how many megatons of TNT?
   2. This amount of energy is equivalent to how many times the world's power use in one hour?
3. Suppose a star is 8 pc away.
   1. How many light-years is that?
   2. How many miles is that?
   3. What parallax, in seconds of arc, does this star have?
   4. How long does it take for a radio message to travel from the Earth to the star?
4. How many times more massive is the Sun compared to the Earth?
5. How many times farther is 1 light-year than 1 AU (astronomical unit)?
6. Suppose there are about 1000 other intelligent civilizations in our Galaxy at the present time. What is the average distance between them?