Charles Messier (1730-1817) was a French astronomer who had an obsession with comets. Getting fed up with 'discovering' fuzzy blobs that turned out to be distractions, he made a catalogue of things to avoid in the night sky. His assistant and friendly rival Pierre Mechain assisted him in this task, and eventually he came up with a list of 103. Later astronomers added another 7 he listed (although number 102 was arguably 'bogus') and he was also aware of M110. So, there are arguably 109 or 110 'Messier Objects'.
Well that's almost ten times as many objects as the number of comets he found, and the irony is that Messier's comets faded back into the obscurity of the outer solar system, while his list is a favourite guide to many of the best sights in the night sky!
The list includes several types of object, mostly globular clusters, open clusters, planetary nebulae and galaxies. Most are telescopic objects, but several can be seen with the naked eye, especially from 'dark sky' sites. Here are some examples from the list:
M1, the Crab Nebula, the remnant of a supernova observed by Chinese astronomers in 1054 CE.
|M13, the Great Globular Cluster in Hercules, this spherical cluster of stars orbits our galaxy, the Milky Way, and contains hundreds of thousands of stars. In good conditions it can be seen with the naked eye, through small telescopes it appears as a 'fuzzy' dot but even modest telescopes start to show individual stars.
|M27, the Dumbbell Nebula, is a 'planetary nebula' an expanding cloud of gas thrown off by a white dwarf star.
|M42, the Great Nebula in Orion, an enormous cloud of gas that is slowly condensing and giving birth to new stars in its bright core. You can see it with the naked eye as the bright 'star' in the middle of Orion's sword.
|M51, the Whirlpool Galaxy, is actually two interacting spiral galaxies. The great Irish astronomer Lord Rosse drew a remarkably accurate drawing of M51 in 1845, using his 'Leviathan' telescope which has recently been restored.
M109 is a good example of one of the less famous members of Messier's list. Harder to track down than some of the brighter and bigger objects, like almost all of the objects it is a beautiful and rewarding target to image.