Field guide · Reading the sky
GalaxyMessier and NGC numbers
M 42, NGC 869: catalogue numbers. Charles Messier listed 110 fuzzy things so he would not mistake them for comets; the NGC lists nearly 8,000.
- Messier (M)
- 110 objects, 1774–1781
- NGC
- 7,840 objects, 1888
- Caldwell (C)
- 109 objects, 1995
Charles Messier hunted comets from Paris in the 1700s. Faint fuzzy patches that did not move kept fooling him, so he listed them to avoid: M 1, the Crab Nebula, was the first. His list became the best-loved catalogue in astronomy, because the things he wanted to ignore are the finest sights in the northern sky.
The New General Catalogue (NGC) came in 1888, compiled by John Dreyer from the Herschels’ sweeps and others: 7,840 objects. Its supplements, the Index Catalogues, add another 5,000. “C” numbers are Patrick Moore’s Caldwell list of 109 showpieces Messier missed, including the southern sky he never saw.
Being in a catalogue says nothing about what a thing is. Messier’s list mixes galaxies, clusters and nebulae — and one mistake: M 40 is just two stars.
See it in the sky
Each one opens the sky map pointed at it, for tonight, from where you are.