Cone Nebula and Christmas Tree Star Cluster (NGC 2264). After many overcast nights, I finally got an opening in the clouds on Monday night. I checked my planetarium program and saw that the Cone Nebula and Christmas Tree Star Cluster would be nearly directly overhead at about 10:00 PM, unfortunately, so would be a half moon. So I finally got started and was able to shoot three hours of 180-second exposures in narrow band (to filter out the nearby half-moon diffused light) through Hydrogen-alpha, Sulfur II, and Oxygen III filters.
The Cone Nebula, seen in the lower left in the image, is a tendril of one of the many background, relatively dense clouds between us and the central region of our Milky Way Galaxy. The black in this image is not the blackness of space but rather a relatively (for interstellar space) dense set of molecular clouds composed of mostly Hydrogen II molecules, shielding us from what otherwise would be a deadly stream of radiation emitted from the Milky Way's central black hole. It lies about 2,700 light-years away in the constellation of Monoceros (the Unicorn). It appears to pass directly overhead in late winter here in the mid-latitudes of earth's northern hemisphere.
The tip of the "cone" is a ball of dense molecular gas in the process of collapsing into a star cluster. The density of that ball has shielded the molecular cloud in its shadow from the intense radiation of 15 Monoceros, the apparently enormous and very bright star seen in the lower left center of the image. Near 15 Mon. is a cloud of gas being illuminated by the blue light of the young star cluster known to astronomers as "The Christmas Tree Cluster" (NGC 2264), with 15 Mon serving as the top of the tree with the group of stars to its lower right appearing as the base of the Christmas Tree. Just above the Christmas Tree can be seen the "Fox Fur" nebula, so named because of its wavy, fur-like appearance. The lower part of the large nebula is fluorescing in the deep red of Hydrogen-alpha as the clouds from which the star cluster was formed are both being blown away and excited into fluorescence by the radiation emitted by the young, highly energetic stars.
In the upper right quadrant of the image can be seen the somewhat older and considerably farther away NGC 2259 star cluster, about 10,500 light-years from earth. The red star in the upper right is HR 2438, a red giant, about 2,500 light-years from us and 200 times the size of our sun, emitting about 6,000 times the energy of old Sol, but its mass is only about 1.2 times that of our sun. It is unstable and pulses noticeably. In about 8 billion years, our sun will probably be similar in size and behavior as it approaches the end of its life. In contrast, the relatively bright red star in the upper right, HR 2426, is only about 500 light-years from us, although it, too, is a red giant, giving off about 55 times the light of Sol. The bright star just off the tip of the Cone appears to be close to it but is actually a blue giant, about 1,000 light-years closer than the Cone, about 1,200 light-years from us, and is, like most stars, part of a multi-star system as it is orbited by one or two other stars.