19-04-2008 Messier’s List (133)

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Simon Kenny
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Location: Shannon, Co. Clare, Ireland

19-04-2008 Messier’s List (133)

Post by Simon Kenny » Fri Jan 02, 2009 4:23 pm

Messier’s List (133)

Charles Messier’s name is one of the best known in astronomy. Born in Lorraine, France, in 1730, his interest in astronomy began as a teenager when he observed the appearance of a six-tailed comet in 1744 and an annular eclipse of the Sun from his home town four years later. (Warning: do not use a telescope or binoculars with the Sun above the horizon — instant blindness will occur).

His passion was to find and observe the movements of comets. Comet searches were hampered for him and others by comet-like fuzzy objects in the sky frequently mistaken for comets by inexperienced observers. To reduce the number of false discoveries, Messier compiled a catalogue of the fuzzy objects that were likely to be mistaken for comets. In 1774, he produced his original list of 45 such objects, increasing the number to 103 by 1781. Subsequently, Messier listed another seven objects, but never formally added them to the list. These are usually accepted as part of Messier’s list, bringing the total to 110 objects. Objects in the Messier list are identified with the prefix ‘M’ followed by its number in the catalogue: for example, M1, in Taurus, a rapidly expanding remnant of a supernova explosion witnessed by Chinese astronomers in 1054 AD.

The Messier catalogue contains a wide variety of celestial objects, all well outside our Solar System, and composed of various combinations of gases, star clusters, galaxies and supernova remnants. When the newcomer has seen and studied the planets in our Solar System, the Messier catalogue always beckons as the next challenge. The reasons are simple. First, Messier studied the skies with small telescopes, the type amateurs today would use, so the objects are fairly easy to find and identify. Also, they are all visible from mid-latitudes in the Northern hemisphere. Secondly, the catalogue contains a wide variety of deep-sky objects:
· Galaxies, like M101 in Ursa Major, which looked spectacular in the Hubble photo after its optics were fixed in 1993, or our neighbour, the Andromeda Galaxy M31, the furthest object we can see with the unaided eye at 2.2 million light years away; or the Whirlpool Galaxy, (M51), observed by Lord Rosse through his ‘Leviathan’ telescope from Birr, in 1845.
· Nebulae, like the Ring Nebula (M57), in Lyra, so named for the ring of cast-off gases from the death of a star seen at its centre, or the magnificent M42, a star forming nebula in Orion’s ‘sword’, visible to the unaided eye.
· Star clusters: these include open clusters like the Pleiades, M45, in Taurus, unmissable on a clear winter’s night, or the Omega cluster, M17, in Saggitarius. A small telescope reveals a magnificent, tightly-knit globe of stars, bound together by mutual gravitational attraction.

In recent years, the ‘Messier Marathon’ is becoming popular, where intrepid telescope owners gather in the nights of late March and early April to observe all 110 Messier objects on one night between dusk and dawn.

There are more recent, comprehensive and better organised catalogues of the stars, but Messier remains the favourite for amateur astronomers.

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