The Horsehead nebula and Flame nebula are great examples of two different types of nebulosity. The Horsehead is a dark nebula and gains it shape as its dense molecular cloud blocks light from stars within and from behind. The Flame nebula on the other hand is an emission nebula whose gases fluoresce from the radiation of hot stars. Both objects lie in the constellation of Orion at a distance of 1,500 light-years.