Melotte 15 is an open star cluster located in the center of the much larger Heart Nebula (IC 1805). It lies in the northern constellation Cassiopeia approximately 7,500 light-years distant. The average age of the massive type O and B stars in the cluster is estimated to be only about 1.5 million years. The cluster is surrounded by clouds of dust and gas. The intense radiation of these extremely hot OB stars illuminates and excites the dust and gas revealing the spactular features and formations associated with Melotte 15. A monochrome Hydrogen Alpha (H-alpha) image of Melotte 15 may be viewed here.
The image above is known as a mapped, or false, color image and was acquired using narrowband filters. It was assembled using the standard Hubble palette with SII mapped to Red, Ha mapped to Green and OIII mapped to Blue.