Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2021 April 28

                  North Star: Polaris and Surrounding Dust
                    Image Credit & Copyright: Bray Falls

   Explanation: Why is Polaris called the North Star? First, Polaris is
   the nearest bright star toward the north spin axis of the Earth.
   Therefore, as the Earth turns, stars appear to revolve around Polaris,
   but Polaris itself always stays in the same northerly direction --
   making it the North Star. Since no bright star is near the south spin
   axis of the Earth, there is currently no South Star. Thousands of years
   ago, Earth's spin axis pointed in a slightly different direction so
   that Vega was the North Star. Although Polaris is not the brightest
   star on the sky, it is easily located because it is nearly aligned with
   two stars in the cup of the Big Dipper. Polaris is near the center of
   the eight-degree wide featured image, an image that has been digitally
   manipulated to suppress surrounding dim stars but accentuate the faint
   gas and dust of the Intergalactic Flux Nebula (IFN). The surface of
   Cepheid Polaris slowly pulsates, causing the star to change its
   brightness by a few percent over the course of a few days.

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