Expert: James Gort - 9/5/2007

Question
QUESTION: How long does it take for the images of the stars in the sky to get here?

ANSWER: Hi Rob,

The time it takes for light from stars to reach us depends on how far they are away.  The nearest star is about 4.2 "light years" away, so light takes 4.2 years to reach us.  The farthest we can see with our naked eyes is the Andromeda Galaxy, a collection of 100 billion stars, located 2 million light years away.  So the images of stars from that object take 2 million years to reach us.

Hope that helps.

Prof. James Gort

---------- FOLLOW-UP ----------

QUESTION: My follow up quest is very simple, does our solar system move as a unit through the galaxy?

Answer
Hi Rob,

The sun has a proper motion and moves in the arm of our Galaxy (towards the star Vega in Lyra), and all the stars in the neighborhood (including the sun) make a long trek around the galactic center.  The planets revolve about the sun and so are carried with the sun as it moves in the Galaxy.  So the planets actually carve out helical patterns in space as they travel with the sun.  So, yes, the solar system does move as a unit through the Galaxy.

Prof. James Gort