Why do we have “seasonal” constellations?

If you’ve been visiting Lie Back, Look Up for awhile (or any other stargazing sites), you’ve probably been reading about the different constellations that you can view each season. You might also be wondering why we see different constellations each season. Understanding this explanation involves visualizing the Earth-Sun relationship in our solar system, as well as our solar system’s position in the Milky Way Galaxy.

It is helpful to remember that the stars are always up in the sky, we’re just not able to see them during the day due to the brightness of the sun. Without the sun shining during the day, we would be able to see the winter constellations during the daytime in the summer (and vice versa). Because the Earth changes position around the sun throughout the year, we get a different view of the stars in the Milky Way Galaxy during different times of the year.

Looking at the drawing above, you can see that on December 21st, we are able to see the stars in the constellation Gemini at night. We would not be able to see the stars of Sagittarius on December 21st, because they would be in the daytime sky. If you are looking to explain this to your kids, it is a great idea to “act out” the drawing above. Print out pictures of the constellations in the drawing and place them around the room. Use a basketball to model the sun in the center. They can rotate to experience day and night, and walk around the sun to model the orbit throughout the year. Have them stop in different positions throughout the year, and ask them which constellations they would be able to see at night. They will have to spin around in their position to face away from the sun, in order to view the nighttime constellations.

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