Symbiotic Star R Aquarii
This illustration depicts one possible explanation for R Aquarii's 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 star's outer layer.