The stars that we see at night change.
As the earth orbits the sun, the part of the night sky that is in our view changes. What this means is that most of the star patterns, or constellations, that we see on a summer night are different from those that we see in the winter, according to Space.com. In other words, in the summer, we can see the stars that during the winter were in our daytime sky, and thus were invisible to us.
Of course, this change in which stars we see doesn't happen all at once. The change in the night sky is subtle from night to night, But, as the season progresses, reports Space.com, a given star sets about 4 minutes earlier each night, so over a month, that means it sets two hours earlier. Gradually, the stars that were low over the western horizon during the early evening hours eventually disappear entirely from our view over a few weeks and their place is taken up stars that earlier were higher in the sky at sundown.
Since the planet completes a circle every year, patterns and constellations re-emerge on schedule every season. For example, it's a great time to see the Big Dipper in the summer.
(Photo by David McNew/Getty Images)