According to Burnham's Celestial Handbook, the best estimate of the distance to the Rosette Nebula is approximately 2,600 light-years, which would put the size of the nebula itself at about 55 light-years in diameter! If this distance estimate is correct, this is one of the largest nebulae on record. Higher resolution images than that attainable through my little 400mm f/2.8 lens on Fujicolor 800 film record numerous dark spots throughout the nebula. These "Bok Globules" are though to be concentrations of gas in the process of forming stars. The star cluster at the center of the nebula is thought to have either exhausted the supply of dust and gas at the heart of the nebula or blown it away by their stellar wind when they formed, thereby creating the dark area you see here. Perhaps one day, so many stars will form in this region of space, that there will be no nebula left.