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Earth, Moon, and the Sun

The star that stays still

Watch the night sky for hours. One star seems to stay in its place.

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The idea

A group of stars, and the Pole Star beside it.
Step 1 of 3
  1. A group of stars, and the Pole Star beside it.
  2. Six hours later, the group has turned a quarter of a circle.
  3. Each star leaves a curved trail round the Pole Star.

The Pole Star sits almost over Earth's north pole. So it hardly moves. Other stars circle it.

A full circle is 360 degrees. The sky seems to turn 15 degrees every hour. A long photograph shows each star as an arc, a curved line. These arcs are star trails.

The Pole Star is seen from the north half of Earth.

Watch out!

The Pole Star is not the brightest star. It is the one that seems not to move.

Jump to lesson

This track

  1. 0 Start here
  2. 1 Earth is doing two things at once
  3. 2 The Moon keeps one face turned to us
  4. 3 When three line up, one shades another
  5. 4 The Moon shades a patch of Earth
  6. 5 Earth shades the Moon
  7. 6 Why it is not every month
  8. 7 One is safe to watch, the other never is
  9. 8 Checkpoint: motions, the Moon and eclipses
  10. 9 Why the Sun seems to move
  11. 10 Day here, night there
  12. 11 The star that stays still
  13. 12 Checkpoint: the turning sky
  14. 13 The night sky changes through the year
  15. 14 The tilt makes the seasons
  16. 15 The longest and shortest days
  17. 16 Checkpoint: the year, the tilt and the seasons
  18. 17 The big picture
  19. 18 Track quiz

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