Symbiotic star R Aquarii (artist's impression)

This illustration depicts one possible explanation for R Aquariiàs semi-periodic outbursts. The peculiar behavior of R. Aquarii suggests that the red giant star in the R Aquarii system may spill some of its mass onto the companion - a common mechanism proposed for most nova-like outbursts. The mass transfer process may form an accretion disk: a swirling, flattened vortex of hot gasses that spiral down onto the hot companion. The disk may periodically erupt when the companion becomes overloaded with in-falling material. These explosions may happen only periodically when the white dwarf orbits close enough to pull in material from the staràs outer layer.