Do the stars move in the sky ?

1 answer

Meenakshi Tripathi February 22, 2017

The stars has their own motion in space called "Proper Motion".The stars are in motion because they are moving along the center of their galaxy.But as the stars are very far away from us and the universe is very big so the motion of star is almost unnoticeable. The star with the highest proper motion is Barnard’s Star. It moves 10.3 seconds of arc per year, meaning it takes about 180 years for it to move the diameter of the full Moon in our sky.

Our Galaxy, like all other spiral galaxies is rotating. The stars move in orbits around the center of the Galaxy.

Stars also have some random motions - they don't orbit the galaxy in exact circles. This random motion usually amount to a few tens of km/s in some direction.

Though all objects rotate in the sky, the observed path, stars make in the sky depend on the observer's latitude.These different ways of classifying stars are :

Rise and Set Stars : During the rotation of the earth, some stars rise from below the eastern horizon and later set below the western horizon. Appropriately enough, these stars are called rise and set stars.

Circumpolar & Never-Rise Stars : Stars near the celestial poles make small circles and may not pass the horizon plane. If they are always above the horizon they are called circumpolar stars. If they are always below the horizon, they are never rise stars. Circumpolar stars in the northern hemisphere are never-rising stars of the southern hemisphere and vice versa.

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