Have you ever noticed that your favorite constellation is not always visible in the night sky? For example, the belt of Orion the Hunter is easy to spot in the winter, but nowhere to be seen in the summer. Where do the stars go? The short answer is that they are still out there shining during the day when you can’t see them.
To understand, remember that the earth rotates on its axis every day, while revolving around the sun every year and you can only see the constellations at night, when your part of the earth is facing away from the sun.
As the Earth orbits around the Sun, constellations move slowly to the west over the course of a year and we see different parts of the sky at night because, as the seasons change, we are looking in a different direction in space. From our spot on earth, the stars appear to rise in the east, cross the sky, then set in the west.
It is like riding on a merry-go-round that takes a year to complete one revolution. As you ride around, you see different parts of the amusement park (universe) pass before our eyes. The part of the universe that we can see depends on which direction the earth is facing at night and where we are in space as the earth orbits the sun.
You have to wait until late summer to see my favorite constellation Delphinus the Dolphin. Greek mythology states that a dolphin was sent by the sea god Poseidon to find Amphitrite, the mermaid he wanted to marry. Visit Name a Star to dedicate a star for a loved one in your favorite constellation.
As our earth whirls through space around the sun, its motions cause night and day and the four seasons. According to our clocks, there are 24 hours in a day, however the earth actually turns on its axis every 23 hours 56 minutes. That 4 minute difference causes the stars to rise and set 4 minutes earlier every night. After a year, we are back where we began 365 days earlier with the same stars returning for our next trip around the sun.