Posted by **Lauren** on Sunday, April 19, 2009 at 3:22pm.

How long an exposure would a photographer need to photograph star trails that are complete circles? Why?

The star Sirius is 4.3 light years from Earth. Determine the distance to Sirius in km and in astronomical units.

THe moon's average distance from Earth is about 380,000 km. How long does it take moonlight to reach Earth? HELP!!!!!!

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