Red supergiant, component of an eclipsing variable star, which changes its apparent brightness from 4.9 mag to 5.7 mag over a period of 20 years. It was once considered the largest known star in the observed part of the universe. It has a diameter 2,400 times larger than the Sun, with an average density only one three-millionth of the density of water. Its distance from Earth is 5,000 light-years.