The centre of the Rosette Nebula (NGC 2237) in Monoceros is swept clear of matter by radiation from the young open star cluster (NGC 2244) within.
The Rosette Nebula is a H-II region, a star-forming region with clouds of gas and dust and is probably no more than a million years old. At a distance of about 5000 light-years and a diameter of 130 light-years, it appears relatively large in the sky, about 80 x 60 arc minutes. The mass of the nebula is estimated at around 10'000 solar masses.
It is best to watch under a dark sky with binoculars or in a telescope at low power.
