Question

When we see a star in the night sky, we are actually seeing how it was sometime in the past. This is because light takes time to travel from the star to Earth. Light travels 9.5 × 1015 m in one year. This distance is called 1 light year. When an astronomer sees the star Betelgeuse, which is approximately 6.08 × 1018 m from Earth, how long ago did the star appear the way it does to her today?

Answer 1

Solution -

The correct answer is  640 years

Step by Step Solutions -

The speed of light to travel some distance = 9.5 × 1015 m /year

Star Betelgeuse is at a distance of 6.08 × 1018 m  

The time taken by light to travel = distance /speed

= 6.08 × 1018 m  /9.5 × 1015 m /year

= 640 year.  

Answer 2

9.5 x 1015 = 9642.5
6.08 × 1018 = 6189.44
  If you take these two problems, and then subtract, and find out the difference between the two distances, then you should be able to get your answer.

 Hope this helps!