Today’s Sky Map

Spot the stars and planets, and simulate the changing sky!

The Sky on at ()

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Did you know ?

Every evening, the stars in the sky return to the same place 4 minutes early because the Earth’s movement in its orbit around the sun gives us a slightly different background of stars each night. These 4 minutes represent the difference between the length of a day (24 hours) and that of an earth’s rotation (23 hours and 56 minutes). Scroll the sky day by day with the next day button to see that the stars are rising a little earlier each evening.

Why is the sky constantly changing?

Because of the movements of the Earth:

As the Earth rotates on itself, we see the sky scrolling as if we were on a ride: the whole sky seems to turn the hours around a point near Polaris, the North Star (center of the map). This causes the “rises” and “sets” of the stars. In addition, the stroke of the Earth around the Sun shows us a different portion of the sky depending on the time of year.

Because of the movements of the celestial bodies themselves:

The Sun, Moon, planets, have a perceptible movement over days (or weeks) to the background of stars while stars are so distant that they appear stationary in a human life.