1. Write the following numbers using a scientific notation (e.g. 125=1.25x 102 ) a) 350= b) 157500= Answer: 2. A star is 230 light years away. How many years ago the light we see tonight left the star? Answer: 3. Light travels 3 x 105 kilometers every second. That number in words is _________ kilometers per second. Answer: 4. How many years does it take light to reach us from a star that is 10 light years? Answer:

5. Polaris, commonly known as the North Star, is the closest relatively bright star to the north celestial pole. It lies at an estimated distance between 323 and 433 light years from Earth. Express the above distance in AU (Astronomical Units) knowing that 1 light year= 63241.0771 AU.