VW Hydri is a

dwarf nova A U Geminorum-type variable star, or dwarf nova (pl. novae) is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwa ...

of the SU Ursae Majoris type in the deep southern constellation

Hydrus Hydrus is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm (14 in) d ...

; a star system that consists of a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

and another generally cool star. It is one of the brightest

e systems in the sky. These systems are characterised by frequent eruptions and less frequent supereruptions. The former are smooth, while the latter exhibit short "superhumps" of heightened activity. The white dwarf sucks matter from the other star onto an

accretion disc An accretion disk is a structure (often a circumstellar disk) formed by diffuse material in orbital motion around a massive central body. The central body is typically a star. Friction, uneven irradiance, magnetohydrodynamic effects, and other ...

and periodically erupts, reaching

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

8.4 in superoutbursts, 9.0 in normal outbursts and remaining at magnitude 14.4 when quiet. Normal outbursts occur every 27.3 days and last for 1.4 days, while superoutbursts happen 179 days and last for 12.6 days.

References

Hydrus (constellation) Dwarf novae Hydri, VW {{var-star-stub