Orion nebula. Hubble Space Telescope mosaic of the Orion nebula (M42; NGC 1976), which is 1500 light years away in the constellation Orion. This is one of the most detailed astronomical images ever produced (as of 2006). It shows thousands of stars never seen before in visible light. Nebulae are huge clouds of interstellar gas and dust. This is an emission nebula, a region of starbirth. It glows red due to the ionisation of the hydrogen gas it contains by radiation from four hot young stars, the trapezium stars, at its core. M42's smaller neighbour M43 (NGC 1982) is seen at top left.