... Runaway Star . ... Like a ship plowing through the interstellar medium, runaway star HD 77581 has produced this graceful arcing bow wave or "bow shock" - compressing the gaseous material in its path. ... On the far side of our Galaxy, gas clouds explode away from a small black hole. ... Some of the stars that form the constellation of Orion are part of a giant gas cloud complex that stretches over 100 light years and appears more than 50 times the diameter of the Moon. ... The Comet and the Galaxy ....