largest known star

VY Canis Majoris (VY CMa) is a red hypergiant located in the constellation of Canis Major. This is the largest known star and one of the most luminous stars known.

Roberta M. Humphreys (2006) estimates the radius of VY CMa is between 1800 and 2100 solar radii. If our sun were replaced with such a star, its surface could extend to the orbit of Saturn. If we take its radius to be that higher figure of 2100 solar radii, it would take more than 8 hours for light to travel around its circumference. If it were possible for a human to walk on the surface of Canis Majoris, at 3 miles an hour for 8 hours a day, it would take him or her 650,000 years to walk the entire circumference (compared with 2 years 11 months to complete the same task on the Earth).

Object Name:
VY Canis Majoris
Object Description:
Variable Star with Circumstellar Nebula
Position (J2000):
R.A. 07h 22m 58s.33Dec. -25° 46' 3".2
Constellation:
Canis Major
Distance:
Approximately 5,000 light-years (1.5 kiloparsecs)
Dimensions:
These images are roughly 35 arcseconds (0.85 light-years or 0.25 parsecs) across.

VY Canis Majoris Credit: NASA, ESA, and R. Humphreys (University of Minnesota)