Variable star

For the astronomical object, see variable star. Variable Star is a 2006 novel written by Spider Robinson based on the surviving seven pages of an eight page 1955 novel outline by the late Robert A. Heinlein. It describes the coming of age of a young musician who signs on to the crew of a starship as a way of escaping from a failed romance.
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A variable star is a star that undergoes significant variation in its luminosity. In contrast, most stars have little variation in luminosity, such as the sun, which undergoes relatively little variation in brightness (usually about 0.1% over an 11 year solar cycle).Broadly speaking, variable stars are of two types:stars that are intrinsically variable, that is, their luminosity actually changes, for example because the star periodically swells and shrinks;eclipsing and rotating variables, where the apparent changes in brightness are a perspective effect.
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Noun
1. a star that varies noticeably in brightness
(synonym) variable
(hypernym) star
(hyponym) Polaris, North Star, pole star, polar star, polestar

Any star whose luminosity varies. The variations can be intrinsic because of internal processes or can be extrinsic due to eclipses and other phenomena. The variations can also be irregular or periodic. If periodic, the timescale may be just a few hours or may be several years. There are many kinds and classifications of variable star. For example, Mira-type variables have relatively long periods but cepheid variable stars have periods of between one and one hundred days. Irregular variables which are sometimes referred to as cataclysmic variables are novae or supernovae . Other irregular variable stars our those which are currently in their T Tauri phase . Extrinsic variables are caused by the rotation of stars with non-uniform brightness or by eclipses in eclipsing binaries . The variation in brightness of all the various forms of variable star, can be plotted on graphs of brightness against time. The resulting graph is known as a light curve.

Eng: variable star
Urdu: مُتغیر سِتارہ ۔ نجم مُتغیرہ ۔ وہ سِتارہ جِس کی چمک مُستقل وقفوں پر سلسلہ وار سُکڑاوٴ اور پھیلاوٴ کے باعِث گھٹتی بڑھتی رہتی ہے ۔