Gamma Doradus (Gamma Dor, γ Doradus, γ Dor) is the third brightest star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 of Dorado. It has an apparent visual magnitude of approximately 4.25 and is a variable star

Variable star

A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...

, the type star of the class of Gamma Doradus variables. These stars, like γ Doradus, are pulsating variables which vary in brightness by less than a tenth of a magnitude owing to nonradial gravity wave

Gravity wave

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media which has the restoring force of gravity or buoyancy....

oscillations. The magnitude of γ Doradus itself has been observed to have two sinusoidal variations with periods of approximately 17.6 and 18.2 hours. There is also some additional unexplained, apparently random fluctuation.