Açıklama
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 bright 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, a digital composite of hundreds of exposures that brings out faint gas and dust of the Integrated Flux Nebula (IFN) all over the frame as well as the
globular star cluster
NGC 188 on the far left. The surface of
Cepheid Polaris slowly
pulsates, causing the famous star to
change its brightness by a few percent over the course of a few days.
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