Which of the following correctly states the luminosity-distance formula?

If your mass is 60 kg on Earth, what would your mass be on the Moon? 

All the stars in this photo are at about the same distance from Earth (some 25,000 light-years away). Which stars in this picture are the largest in size (radius)?

This photo shows an object located in the halo of our Milky Way galaxy. What kind of object is it?

Look again at the loop of hot gas in this X-ray image. Suppose we took another photo looking at the same place 1 hour later. What would we se

In the formula E = mc 2, what does E represent? 

Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores. 

Absolute zero is 

Which is the strongest of the fundamental forces in the universe? 

One light-hour is the distance that light travels in an hour. How far is this, in kilometers? (Recall that the speed of light is 300,000 km/s.)