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:
“Walked forth to ease my pain
Along the shore of silver streaming Thames,
Whose rutty bank, the which his river hems,
Was painted all with variable flowers,”
—Edmund Spenser (1552?–1599)
“For rigorous teachers seized my youth,
And purged its faith, and trimm’d its fire,
Show’d me the high, white star of Truth,
There bade me gaze, and there aspire.
Even now their whispers pierce the gloom:
What dost thou in this living tomb?”
—Matthew Arnold (1822–1888)