Monoceros nebular complex
What do the following things have in common: a cone, the fur of a fox, and a Christmas tree? Answer: they all occur in the constellation of the unicorn (Monoceros).
Just below the center of the left panel of this 4 degree wide mosaic is a star forming region cataloged as NGC 2264. The complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. Outlined by the red glow of hydrogen gas, the cone points toward the left and bright, blue-white S Monocerotis. Itself a multiple system of massive, hot stars S Mon is adjacent to bluish reflection nebulae and the convoluted Fox Fur nebula. Given their distribution, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The curious compact cometary shape at the bottom of the left panel is known as Hubble's Variable Nebula.
Expansive dark markings on the sky are silhouetted by a larger region of fainter emission with yellowish open star cluster Trumpler 5 near the center of the frame.
On the right panel lays several interesting objects as well, with the largest bluish reflection nebula at the utmost right being IC2169, known as Dreyer's Nebula. The color comes from scattered star light of the illuminating stars which are either in or behind it. The nebula is blue for the same reason our sky is blue. The tiny molecules of dust and gas scatter blue light better than the other colors due to its short wavelength. It matters little what color the illuminating stars are, as long as they emit some blue light the nebula was take on a blue color same as the somewhat yellow sun still results in our blue sky. IC2169 is thought to be part of the same huge cloud of dust and gas that includes the Cone Nebula as well as the Christmas Tree, laying at the same distance and considerably further away than the nearby Orion Nebula complex. The remaining bright reflection nebula are NGC 2245, NGC 2246 and IC446 which seems connected to the Dreyer's Nebula by a bridge of dust (text adapted from APOD).
Two panel mosaic, Apo TEC140 (140/f7.2) - FLI Proline 16803 - total exposure Ha(480m) L(400m) R (270m) G (270m) B (270m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia. Spikes added with StarSpikes Pro 4.
