The ever-changing R Aquarii

This video shows the evolution of a chaotic and fascinating binary star system named R Aquarii. The time lapse begins with observations from the Nordic Optical Telescope taken in 1997. In the 15 years since that image was taken the system has been observed by many other telescopes, including ESO’s Very Large Telescope. This video lapses between a selection of these images, showing the expansion and evolution of the material surrounding R Aquarii.

R Aquarii is a so-called “symbiotic binary”, comprising two stars surrounded by a large, dynamic cloud of gas (a nebula). Systems like this contain two stars in an unequal and complex relationship. R Aquarii is made up of one hot white dwarf and one red giant. The red giant is losing matter to its small companion and occasionally ejecting matter in weird spurts, loops and trails, forming the intriguing shapes seen here.

There is a lot going on between the performers in this cosmic double act. The red giant is a variable star, with a brightness that changes by a factor of 750 every year and three weeks. The faint nebula is named Cederblad 211 and is thought to be the result of a violent nova 250 years ago. Also visible is a narrow, vertical, S-shaped feature, with blobs of superheated material.