Messier Catalog Pdf

[Paulette Dzurilla]

TheMessier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his Catalogue des Nbuleuses et des Amas d'toiles (Catalogue of Nebulae and Star Clusters). Because Messier was interested only in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. This list, which Messier created in collaboration with his assistant Pierre Mchain, is now known as the Messier catalogue. The Messier catalogue is one of the most famous lists of astronomical objects, and many objects on the list are still referenced by their Messier numbers.[1] The catalogue includes most of the astronomical deep-sky objects that can be easily observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers.[2]

A preliminary version of the catalogue first appeared in 1774 in the Memoirs of the French Academy of Sciences for the year 1771.[3][4][5]The first version of Messier's catalogue contained 45 objects, which were not numbered. Eighteen of the objects were discovered by Messier; the rest had been previously observed by other astronomers.[6]By 1780 the catalogue had increased to 70 objects.[7] The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.[8][4]However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.[9]

The catalogue consists of a diverse range of astronomical objects, from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Further inclusions followed; the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.[10]

The first edition of 1774 covered 45 objects (M1 to M45). The total list published by Messier in 1781 contained 103 objects, but the list was expanded through successive additions by other astronomers, motivated by notes in Messier's and Mchain's texts indicating that at least one of them knew of the additional objects. The first such addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding a note Messier made in a copy of the 1781 edition of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.[11] M102 was observed by Mchain, who communicated his notes to Messier. Mchain later concluded that this object was simply a re-observation of M101, though some sources suggest that the object Mchain observed was the galaxy NGC 5866 and identify that as M102.[12]

Messier's final catalogue was included in the Connaissance des Temps pour l'Anne 1784 [Knowledge of the Times for the Year 1784], the French official yearly publication of astronomical ephemerides.[8][4]

All Messier objects can be seen in small and medium telescopes. Some, like the Pleiades (M45), Praesepe (M44), and the Ptolemy Cluster (M7), are even visible to the unaided eye. All 110 objects are visible to observers in mid-northern latitudes.

The Crab Nebula (M1) is a supernova remnant approximately 6,500 light years away in the constellation Taurus. It is the remnant of the historic supernova SN 1054, observed from July 4, 1054, to April 6, 1056. It appears near the blue giant star Tianguan (Zeta Tauri), which marks the northern horn of the Bull. The remnant has an apparent size of 7 by 5 arcminutes and a physical diameter of about 11 light years. With an apparent magnitude of 8.4, it is easily seen in small telescopes.

NGC 7089 (M2) is a globular cluster 55,000 light years away in the constellation Aquarius. It has an apparent magnitude of 6.3 and is 16 arcminutes across. The cluster spans 175 light years and contains about 150,000 stars. It has an estimated age of 13 billion years. It is one of the globular clusters believed to be part of the Gaia Sausage (Gaia Enceladus), the hypothesized remains of a dwarf galaxy that was absorbed by the Milky Way 8 to 11 billion years ago.

NGC 5272 (M3) is a globular cluster 33,900 light years away in the constellation Canes Venatici. It appears almost exactly halfway between Arcturus and Cor Caroli. The cluster has an apparent magnitude of 6.2 and an apparent size of 18 arcminutes. It contains about 500,000 stars and has a physical radius of 90 light years. Its estimated age is about 11.39 billion years.

NGC 6121 (M4) is a globular cluster 7,200 light years away in the constellation Scorpius. It appears only 1.3 degrees west of Antares. The cluster is about 75 light years across. With an apparent magnitude of 5.9 and an apparent size of 26 arcminutes, it is easily observed in small telescopes. It has an estimated age of 12.2 billion years.

NGC 5904 (M5) is a globular cluster 24,500 light years away in the constellation Serpens. It has an apparent magnitude of 5.95 and an apparent size of 23 arcminutes. It appears 22 arcminutes northwest of the magnitude 5.10 star 5 Serpentis. The cluster is 160 light years across. It has an estimated age of 10.62 billion years.

NGC 6333 (M9) is a globular cluster 25,800 light years away in the constellation Ophiuchus. It has an apparent magnitude of 7.9 and an apparent size of 9.3 arcminutes. It appears next to a dark nebula catalogued as Barnard 64 and two fainter globular clusters, NGC 6356 and NGC 6342. The brightest stars in M9 can be observed in a small telescope. The cluster has a radius of 45 light years. Its estimated age is 12 billion years.

The Wild Duck Cluster (M11) is an open cluster 6,120 light years away in the constellation Scutum, the Shield. It appears near the tail of the Eagle (Aquila). It was nicknamed the Wild Duck Cluster because it vaguely resembles a flying flock of ducks. The cluster has an apparent magnitude of 5.8 and is 22.8 arcminutes across. It has a tidal radius of 94 light years. The estimated age of the cluster is about 316 million years.

NGC 6218 (M12) is a globular cluster in Ophiuchus. It lies 16,440 light years away and has an apparent magnitude of 7.68. It spans 16 arcseconds across, corresponding to a physical diameter of about 75 light years. M12 appears roughly two thirds of the way from Cebalrai (Beta Ophiuchi) to Yed Posterior (Epsilon Ophiuchi), 5.6 degrees east-southeast of Marfik (Lambda Ophiuchi). The brightest stars in the cluster can be resolved in 8-inch or larger telescopes. The estimated age of the cluster is about 13.8 billion years.

The Hercules Globular Cluster (M13) is a bright globular cluster in the region of the Keystone asterism in the constellation Hercules. It is one of the best-known globular clusters in the northern celestial hemisphere. M13 is about 145 light years across. It appears between the stars Eta and Zeta Herculis, or about a third of the way from Vega to Arcturus. The magnitude 11.7 spiral galaxy NGC 6207 appears in the same area. The Hercules Globular Cluster has an apparent magnitude of 5.8 and lies approximately 22,200 light years away. With an apparent size of 20 arcminutes, it makes a fine target for small telescopes. The estimated age of the cluster is 11.65 billion years.

NGC 6402 (M14) is a globular cluster 30,300 light years away in Ophiuchus constellation. It has an apparent magnitude of 8.32 and stretches across 11 arcminutes of the apparent sky. It has a linear diameter of about 100 light-years. A fainter globular cluster, NGC 6366, lies just over 3 degrees southwest of M14.

NGC 6273 (M19) is a globular cluster about 28,700 light years away in Ophiuchus constellation. It appears 4.5 degrees west-southwest of Theta Ophiuchi. It has an apparent size of 17 arcminutes and an apparent magnitude of 7.47. Its estimated age is 11.90 billion years. The cluster lies only 6,500 light years from the Galactic Centre.

The Trifid Nebula (M20) is an H II region about 4,100 light years away in Sagittarius. With an apparent magnitude of 6.3 and an apparent size of 28 arcminutes, it makes a good target for small telescopes. M20 consists of an emission nebula, a reflection nebula, a dark nebula, and an open star cluster. It has a radius of 21 light years.

NGC 6494 (M23) is an open cluster 2,050 light years away in Sagittarius. With an apparent magnitude of 5.5 and an apparent size of 35 arcminutes, it can be seen in binoculars and small telescopes. It has a radius of 8 light years. The estimated age of the cluster is about 330 million years.

The Small Sagittarius Star Cloud (M24) is a Milky Way star cloud about 10,000 light years away in Sagittarius. It is the densest concentration of stars that can be seen in binoculars. About a thousand stars populate a single field of view. M24 has a radius of about 600 light years. It is one of three Messier objects that are not deep sky objects. Several dark nebulae are found in the same area. They are catalogued as Barnard 92, Barnard 93, Barnard 304, and Barnard 307.

IC 4725 (M25) is an open cluster approximately 2,000 light years away in Sagittarius. It has an apparent magnitude of 4.9 and an apparent size of 36 arcminutes. It is about 13 light years across. Its estimated age is 67.6 million years.

NGC 6694 (M26) is an open star cluster that appears southwest of the Wild Duck Cluster (M11), near the famous variable star Delta Scuti in the constellation Scutum. The cluster lies 5,160 light years away and has an apparent magnitude of 8.0. It is 14 arcminutes across and has a linear diameter of 22 light years, with a tidal radius of 25 light years. It has an estimated age of 85.3 million years.

NGC 6626 (M28) is a globular cluster appearing less than a degree northwest of Kaus Borealis (Lambda Sagittarii) in the constellation Sagittarius. With an apparent magnitude of 7.66 and an apparent size of 11.2 arcminutes, the cluster can be observed in small telescopes. Its brightest stars can be resolved in 6-inch and larger telescopes. The cluster lies approximately 18,260 light years away. It has an estimated age of 12 billion years.

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