9 VY Canis Majoris
The big bang
At 1,420 solar radii, VY Canis Majoris is one of the ten largest stars we know about. Before its radius was determined by the European Southern Observatory’s Very Large Telescope, it was theorised that VY Canis Majoris might even be as big as 2,100 solar radii. This red hypergiant resides in the constellation of Canis Major, about 4,500 light years away from us.
With recorded observations dating back more than two centuries, astronomers have long been aware of its crimson hue and changeable magnitude. It was theorised that it was a multiple star system, but more recent imaging has revealed bright concentrations within a vast surrounding nebula and that it has no stellar companions. Hubble data has revealed that this nebula is structurally similar to at least one yellow hypergiant, prompting suggestions that it might follow this evolutionary route before eventually becoming a Wolf-Rayet star.
It has experienced many localised eruptions, forming loops, arcs and knots of material as it approaches the end of its life. Today VY Canis Majoris has probably shed around half of its mass as it continues to exhaust its nuclear fuel and draws inexorably closer to a likely supernova.