Emission Nebula
A cloud of ionized gas emitting light of various colors, often found in regions of active star formation and contributing to the reddish hues observed in galaxies.
Source: esa.int
APODs including "Emission Nebula"
The Heart Nebula in Hydrogen, Oxygen, and Sulfur
27/08/2017
What powers the Heart Nebula? The large emission nebula dubbed IC 1805 looks, in whole, like a heart. The nebula's glow -- as well as the shape of the gas and dust clouds -- is powered by by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster Melotte 15. This deep telescopic image maps the pervasive light of narrow emission lines from atoms of hydrogen, oxygen, and sulfur in the nebula. The field of view spans just over two degrees on the sky, so that it appears larger than four times the diameter of a full moon. The cosmic heart is found in the constellation of Cassiopeia, the boastful mythical Queen of Aethiopia .