Public index · Astronomy
Messier 42
M42
Measured
Orion Nebula, catalogue designation M42
The Orion Nebula is object 42 in Messier’s catalogue · a name, not a measurement of forty-two.
Documentary plate · Fig. 2
A cavern where stars are still being born. Hubble mosaic of the Orion Nebula. The name M42 is Messier’s list number, not a measured forty-two. NASA, ESA, Hubble, Orion Treasury Project Team, M. Robberto (STScI/ESA).
What it supports
A historical catalogue designation (Messier 1771) for a real, observed nebula (NGC 1976), the nearest large star-forming region.
What it does not
M42 is not a measured quantity of 42. The number is a list position. Later deep images do not make the designation a physical constant.
ExactnessDesignation
FormM42
Unitcatalogue
Strengthhard
When1771