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)
“And though in tinsel chain and popcorn rope
My tree, a captive in your window bay,
Has lost its footing on my mountain slope
And lost the stars of heaven, may, oh, may
The symbol star it lifts against your ceiling
Help me accept its fate with Christmas feeling.”
—Robert Frost (1874–1963)