Astronomy Picture of the Day

Explanation: What's happening in and around the Cave Nebula? To help find out, NASA's orbiting Spitzer Space Telescope looked into this optically-dark star-forming region in four colours of infrared light. The Cave Nebula, catalogued as Sh2-155, is quite bright in infrared, revealing details not only of internal pillars of gas and dust, but of the illuminating star cluster too - all near the top of the image. The red glow around the Cave's entrance is created by dust heated by bright young stars. To the right is Cepheus B, a star cluster that formed previously from the same cloud of gas and dust. Other interesting stars of Cepheus come to light in infrared as well, including those illuminating an even younger nebula toward the image bottom, and a runaway star pushing a bow shock, tinged in red near the image centre. This region spans about 50 light years and lies about 2,500 light years toward the constellation of the King of Aethiopia (Cepheus).