The variable star R Aquarii is in a fact two stars tied in orbit around one another with a period of around 44 years.
The primary star is a variable red giant, meaning it pulsates, changes temperature and undergoes drastic brightness fluctuations on a cycle of about 390 days. The secondary star is a white dwarf that sucks in material from the red giant. Some of the surplus material is sometimes ejected, forming the spectacular loopy nebula.
This kind of white dwarf–red giant binary pairing is known as a symbiotic star.
The image above is composed from several images in different wavelengths taken by the Hubble Space Telescope.
Originally published by Cosmos as A symbiotic star in Aquarius
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