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
Famous quotes containing the words variable and/or star:
“There is not so variable a thing in nature as a lady’s head-dress.”
—Joseph Addison (1672–1719)
“Events, actions arise, that must be sung, that will sing themselves. Who can doubt, that poetry will revive and lead in a new age, as the star in the constellation Harp, which now flames in our zenith, astronomers announce, shall one day be the pole- star for a thousand years?”
—Ralph Waldo Emerson (1803–1882)