Rao, known to Earth astronomy as LHS-2520, is the name of the red sun around which the planet Krypton orbits. Rao is also the name of the personification of that sun, who the Kryptonians worship as a god of light and life, similar to God in Christianity.
The sun was created by a race of gaseous beings called the Sun-Thrivers who drew matter from far galaxies. However, the sun was unstable, so the Sun-Thrivers created planets out of solar matter, using their collective gravity to stabilize the turbulent sun storms. Of all the planets in orbit, Krypton was the most powerful.
Rao was given the idea by Despair of the Endless-another deity, controlling all despair-- to allow the civilization of Krypton to flourish, and then for the planet to be destroyed; and for only one inhabitant to survive. This was considered to be "artful". ("The Sandman: Endless Nights")
New 52 Continuity
Rao is located about 27 light-years from Earth, at LHS-2520. As such Neil Degrasse Tyson was able to organize a worldwide collaboration to use many telescopes in conjunction to get a high-quality image of Krypton's destruction. ("Star Light, Star Bright")