This image, 3.5 degrees wide and 3.5 degrees high, includes the famous Cone Nebula and so much more. It has it all: fluorescing Ha, lanes of obscuring dust, reflection nebulae, Herbig-Haro objects, a rich star field that includes three open clusters, and plenty of historical significance. The region was studied by E. E. Barnard and included in his catalog of "dark objects," and also by Edwin Hubble. Both of these famous astronomers worked together at Yerkes Observatory in Williams Bay, Wisconsin, as their studies in this region progressed.

In his famous catalog of dark nebulae, Barnard cataloged those in this image as entries 37, 38, and 39. In particular, the largest portion of the nebula is Barnard 37, situated below center left of the image. Barnard did not include imagery of this region in his catalog, so it's not completely clear what portions of the nebula he referred to as 38 and 39.

IC 2169 is the large reflection near the left edge of the image. Also called "Dreyer's Nebula," it has the distinction of being erroneously duplicated in the Index Catalog as both entry 2169 and 447. It is accompanied by a trio of smaller reflection nebulae, IC 2167 (also duplicated as IC 446), NGC 2245, and NGC 2247. These all sit on the edge of the inky black Barnard 37.

The ancient open cluster Trumpler 5 (Collinder 105) is in the center of the image. Situated 11,000 light years from us, and significantly reddened by interposed galactic dust, it is an exceptionally old open cluster. Based on the metallicity of its stars, the age of this cluster has been estimated at five billion years, an incredible age for open clusters, which normally disperse after some hundreds of millions of years. In this instance, the mass of the cluster is enough to resist dispersion and retain the bulk of its stars, which have been unable to gain escape velocity from the gravitational interactions within the cluster. Its yellow color is due in part to the age of its stars, as well as reddening from the gas and dust in the region. The brightest member of Trumpler 5 is V493 Mon, a beautiful carbon star.

NGC 2259, a younger and smaller version of Trumpler 5 appears at bottom center. These open clusters are cousins, both approximately the same distance from us. NGC 2259 will not last nearly as long as Trumpler 5. The brilliant star to the left of NGC 2259 is HR 258. At its distance of 127 light years, Trumpler 5 and NGC 2259 are 100 times farther away.

Above and to the right of NGC 2259 is the famous Christmas Tree Cluster region. Shaped like a Christmas Tree, it is an Ha region powered by the massive 15 Monocerotis, also known as S Monocerotis. It has traditionally been considered the source of much of the radiation that powers the Ha emission nebula. NGC 2264 is the cluster of O and B supergiant stars adorning the boughs of the Christmas Tree. Like a Christmas Star, the Cone Nebula graces the apex of the tree. Its striking shape is the result of radiation pressure eroding the dusty cloud in the area.

There are several Herbig-Haro objects within this nebulosity, the result of jets spewing outward from young protostars. While the jets themselves are typically invisible, as they collide with the surrounding environment, they compress and heat the gasses which then glow. Several of their graceful and delicate arches are just above 15 Mon in the image. They are easy to miss, but they tell us that star formation is still very active in this region.

Hubble's Variable Nebula is near the top of the image above the Cone Nebula. It was a favorite of Edwin Hubble for his entire career. He first studied this nebula as a staff astronomer at Yerkes Observatory. Perhaps his most famous image of this object was the first light photograph he acquired with the brand new 200" Hale Telescope. It is a unique object in that it appears to change on relatively short timeframes. The star at its point, R Monocerotis, has clouds of thick dust orbiting it which cast shadows out into the nebulosity. The University of Manitoba has produced a striking animation of the rapid changes in this nebula.

The non-existent NGC 2265 is near the bottom right of the image. A cluster at this location was cataloged by William Herschel in 1932, but the entry seems to be in error. There is no cluster at the location, and there isn't one at any other coordinates that may have been the result of a scribing error, such as numerical transposition or such. The best anyone can figure is that he saw some stars he felt were related there, and made the catalog entry, but nobody else has ever figured out what stars he was looking at.

Image acquired at Prairie Sky Observatory, a facility of Twin City Amateur Astronomers (tcaa.us).