NASA. Symbiotic R Aquarii

Image Credit: X-ray: NASA/CXC/SAO/R. Montez et al.; Optical: Data: NASA/ESA/STScI, Processing: Judy Schmidt (CC BY-NC-SA)
Explanation: Variable star R Aquarii is actually an interacting binary star system, two stars that seem to have a close symbiotic relationship. Centered in this space-based optical/x-ray composite image it lies about 710 light years away. The intriguing system consists of a cool red giant star and hot, dense white dwarf star in mutual orbit around their common center of mass. With binoculars you can watch as R Aquarii steadily changes its brightness over the course of a year or so. The binary system’s visible light is dominated by the red giant, itself a Mira-type long period variable star. But material in the cool giant star’s extended envelope is pulled by gravity onto the surface of the smaller, denser white dwarf, eventually triggering a thermonuclear explosion, blasting material into space. Astronomers have seen such outbursts over recent decades. Evidence for much older outbursts is seen in these spectacular structures spanning almost a light-year as observed by the Hubble Space Telescope (in red and blue). Data from the Chandra X-ray Observatory (in purple) shows the X-ray glow from shock waves created as a jet from the white dwarf strikes surrounding material.

Located 650 light-years away, R Aquarii is a so-called symbiotic binary, comprising two stars surrounded by a large, dynamic cloud of gas (a nebula)Such binaries contain two stars in an unequal and complex relationship — a white dwarf and a red giant.

In a disquieting act of stellar cannibalism, the white dwarf is stripping matter from its larger companion. The tormented red giant and the unstable white dwarf occasionally eject matter in weird spurts, loops and trails.

“The red giant in the R Aquarii system is a type of star known as a Mira variable,” the astronomers said. “At the end of their life, these stars start to pulsate, becoming 1,000 times as bright as the Sun as their outer envelopes expand and are cast into the interstellar void.”

“The death throes of this vast star are already dramatic, but the influence of the companion white dwarf star transforms this intriguing astronomical situation into a sinister cosmic spectacle.”