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Question

Why doesn't the north star appear to move like the other stars?


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Solution

Pole star:

  1. The constellation Ursa Minor, which includes the "Little Dipper" constellation, is where the Pole star is located.
  2. The star at the Little Dipper's handle's tip is the Pole star. However, the Little Dipper is not very bright and might be difficult to spot. It can be easily found by locating the seven stars of the Big dipper in the constellation Ursa Major, commonly known as the Big Bear.
  3. The spin axis of the Earth is a hypothetical line that passes through the Earth.
  4. All places on Earth would seem to circle the axis if you were high above the planet and were gazing straight down along it. From the northern hemisphere of Earth, this axis would point toward a certain star in the sky if you followed it out into space. Since it is located in the direction that the spin axis from the northern hemisphere of Earth points to, we refer to it as the North Star.
  5. Polestar is the brightest star that appears closest to either celestial pole at any given time in the Northern Hemisphere.

An illustrative diagram of the pole star along the Earth's axis is shown below.

Explanation:

  1. The pole star is very distant from Earth and located in a position very near Earth's north celestial pole.
  2. As the pole star is located not far away from the axis of the Earth. It is located about 1° off to the side of the north celestial pole, so it does move a little, creating a colossal arc in the night sky, around which the other stars that are visible from the Earth make wider loops.
  3. The pole star is in the center of a star field. It does not appear to move because the pole star is aligned with the earth's axis.
  4. Due to the rotation of the Earth about its axis, the other stars appear to trace arcs of movement.
  5. The spin axis of the Earth undergoes a motion called precession.
  6. Because of equinox precession, the position of each pole describes a small circle in the sky over a period of 26,000 years.

An illustrative diagram of the precession of the Earth's axis is shown below.


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