Rosette Nebula (NGC 2237)

The Rosette Nebula is located approximately 5,000 to 5,200 light-years from Earth, with distance estimates varying somewhat depending on the measurement method used. It spans roughly 130 light-years in diameter, making it one of the larger emission nebulae visible from the Northern Hemisphere.

The Rosette Nebula is located in the constellation Monoceros, the Unicorn, which sits near the winter hexagon between Orion, Gemini, and Canis Major. The nebula itself is faint and difficult to see visually, typically requiring at least a medium-aperture telescope with a narrowband or Hydrogen-alpha filter under dark sky conditions.

The open star cluster NGC 2244 sits at the center of the Rosette Nebula and is responsible for ionizing the surrounding hydrogen gas, causing it to glow. This cluster of young, hot O-type and B-type stars is estimated to be about 5 million years old, and its stellar winds have carved out the central cavity in the nebula.

The Rosette Nebula is a popular astrophotography target that can be captured with a small refractor (60mm to 80mm aperture) and a cooled astrophotography camera or modified DSLR. A Hydrogen-alpha narrowband filter significantly enhances the nebula's detail, and exposures of several hours total integration time are typically needed to bring out the faint outer filaments.