APOD 4.7 (A Beautiful Trifid)

Since we are getting to the end of this year's APODs (not going to miss dealing with this interface), I thought we could wrap it all up by talking about one of the first constellations we learned in the newest APOD.  M20, or the Trifid Nebula, is a celestial object inside the constellation Sagitarius.  It actually consists of three different types of nebulae: red emission nebulae dominated by light emitted by hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark dust nebulae where dense dust clouds appear in silhouette.  The Trifid has a central red emission nebulae divided into three parts by a few dark dust nebulae, and surrounded by the blue haze of a blue reflection nebulae.