An international collaboration of astronomers, led by Hans Martin Schmid, ETH Zurich captured images of R Aquarii, a binary star system in the Aquarius constellation a mere 650 light-years from earth – a near neighbor in astronomical terms. While most binary stars engage in a graceful gravitational waltz, R Aquarii’s dance is more like a Tango between two passionate and headstrong lovers. The images reveal in the center a red giant on the left, a type of pulsating star known as a Mira variable, because its atmosphere expands and contracts regularly. The images also reveal to astronomers the white dwarf companion on the right – a smaller, hotter, and denser star – which is steadily stripping matter from its dance partner, the red giant. The captured gas is then spiraling in a disk towards the white dwarf, a process that generates two gas jets perpendicular to the disk generating all the clouds.



Occasionally enough matter collects on the surface of the white dwarf to trigger a thermonuclear nova-like explosion spewing vast amounts of matter. The remnants of past nova events can be seen in the tenuous interstellar cloud of dust and gas radiating from R Aquarii.



Schmid, a professor in ETH Zurich’s Institute for Particle Physics and Astrophysics, describes the moment they captured the observation saying, “My team and I were testing and calibrating our instrument at the telescope when we selected R Aquarii as test target. At first, we thought something had shifted in our instruments, but when we realized that what we were observing was real we also observed that the center involved two stars. We were delighted to not only know our instruments were working well, but that the ZIMPOL/SPHERE system at the Very Large Telescope is providing pixel images with the highest spatial resolution currently available in Astronomy.”



R Aquarii was a perfect way for astronomers to test the capabilities of the Zurich IMaging POLarimeter (ZIMPOL), a component on board the planet-hunting instrument SPHERE. The results exceeded observations from space — the image shown here is even sharper than observations from the famous NASA/ESA Hubble Space Telescope.