The Orion Nebula, also known as the M42 or NGC 1976, 
is a diffuse cloud that shines in emission and reflection at the heart 
of the constellation of the same name. It is the most intense nebula visible 
to the naked eye from the northern hemisphere, at night and in the absence 
of light pollution. It can be easily seen with binoculars. 
Its structure occupies a 66 × 60 minute arc of sky, 
four times larger than the full moon. Its size is about 33 light-years in size. 
This object corresponds to the main part of a much larger cloud of gas and dust, 
the Orion cloud, which extends over almost half of the constellation and contains 
in addition the Barnard's loop and the nebula of the Horse Head.