Sometimes the simplest shapes are the hardest to explain. For example, the origin of the mysterious cone-shaped region [ http://antwrp.gsfc.nasa.gov/apod/ap040529.html ] seen on the far left remains a mystery. The interstellar formation, dubbed the Cone Nebula [ http://www.seds.org/messier/xtra/ngc/n2264.html ], is located about 2700 light years [ http://csep10.phys.utk.edu/guidry/violence/lightspeed.html ] away. Other features in the image include red emission [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] from diffuse interstellar hydrogen [ http://antwrp.gsfc.nasa.gov/apod/ap010113.html ], wispy filaments of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap001119.html ], and bright star S Monocerotis [ http://www.aao.gov.au/images/captions/aat014.html ], visible on the far right. Blue reflection nebulae [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] surround the brighter stars. The dark Cone Nebula [ http://www.skyhound.com/sh/archive/jan/NGC_2264.html ] region clearly contains much dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] which blocks light from the emission nebula [ http://www.noao.edu/image_gallery/emission_nebulae.html ] and open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] NGC 2264 [ http://antwrp.gsfc.nasa.gov/apod/ap010424.html ] behind it. One hypothesis [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1985cgd..conf..213B ] holds that the Cone Nebula is formed by wind particles [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] from an energetic source blowing past the Bok Globule [ http://antwrp.gsfc.nasa.gov/apod/ap961229.html ] at the head of the cone [ http://www.sisweb.com/math/algebra/conics.htm ].