The image above is of the central portion of the Christmas Tree Cluster (NGC 2264).  The bright star in the center of the image is designated S Mon and can be seen with the unaided eye in relative dark skies.  The area around the star is filled with glowing gas and dark dust clouds.  The image was captured using a narrow band Hydrogen Alpha filter.  This filter isolates the light from the glowing hydrogen gas of the nebula and enhances the detail of the nebula.  The filter rejects the blue light that is scattered by the dust in the nebula that sometimes mutes or obscures nebular details.  This nebula is an active star forming region of space and lies approximately 2,500 light years from the earth in the direction of the constellation of Monoceros.

¹http://antwrp.gsfc.nasa.gov/apod/ap010424.html