Stellar Variability

Variable Stars

If the fluctuation from a star is large enough to be seen from Earth, the star is classified as a variable star. Variable stars are pretty common. Astronomers identified over 2 million variable stars by the year 2020.

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Intrinsic vs Extrinsic

The two categories of variable stars are intrinsic and extrinsic stars. Intrinsic stars have physical luminescent changes from pulsations, eruptions, swellings, or shrinkings. The other category, extrinsic stars, change in luminosity due to being eclipsed by another star or planet.

Pulsating

Pulsating variables vary in the star's brightness due to the periodic expansion and contraction of the surface layers.

Cataclysmic

Cataclysmic variables are a close binary variable where a white dwarf creates an outburst, or a nova, with the help of a star.

Eruptive

Eruptive variables have violent processes, causing them to vary in brightness

Eclipsing Binaries

Eclipsing binaries are stars that change in brightness. They are a system of two stars that are bound in a gravitational orbit. They fluctuate in luminosity due to the stars eclipsing each other.

Rotating Variables

Rotating variables are stars without a uniform surface brightness or is shaped like an ellipse. Therefore, when the star rotates, it appears to be changing in brightness and luminosity.

Cepheid Stars

These are stars that periodically brighten and diminish. In 1912, Henrietta Swan Leavitt observed that 25 stars located in the Magellanic cloud would begin to brighten and dim at regular intervals of time. Furthermore, the brighter the Cepheid, the longer the period would be.

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