Variable Star
A variable star is a star whose brightess as seen from Earth (its apparent magnitude) fluctuates.
This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either:
- Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks.
- Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it.
Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11 year solar cycle.
Read more about Variable Star: Discovery, Detecting Variability, Variable Star Nomenclature, Classification
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Famous quotes containing the words star and/or variable:
“Our star was brighter perhaps when it had water in it.
Now there is no question even of that, but only
Of holding on to the hard earth so as not to get thrown off,
With an occasional dream, a vision ...”
—John Ashbery (b. 1927)
“There is not so variable a thing in nature as a lady’s head-dress.”
—Joseph Addison (1672–1719)