Key points: Messier and NGC catalogue
M31 (Andromeda Galaxy)
Source :https://www.justinngphoto.com
The invention of telescopes helped amatuer as well as professional astronomers to look deep in the sky, wandering deep sky objects. Star clusters, nebulae and galaxies come under the classification of deep sky objects, unlike individual star or solar system objects. Right now 3 different general catalogs of deep sky objects are available, such as Messier, New General Catalogue (NGC), Index Catalog (IC) etc.
In the 18th century, a french astronomer, Charles Messier, while searching for comets, found a cloudy object (nebula). Then, he started observing such other objects in the sky and kept a catalogue of various clusters (open, Globular), nebulae (diffuse, planetary), galaxy and supernova remnants, known as “Messier catalogue”. This catalogue contains 110 deep sky objects, out of which 96 are imaged by the Hubble telescope till now. These objects have numbers, instead of names, from 1 to 110 and written as ‘M(number)’ or ‘Messier (number)’, for example, M10 or Messier 10.
The NGC catalogue is one of the largest astronomical catalogs of deep sky objects useful for all, from beginner to professional. It was originally compiled in 1888, by John Louis Emil Dreyer, including supernova remnants, nebulae (emission, absorption), star clusters etc. After several revisions (1888, 1895, 1908) and corrections, a complete “New General Catalog and Index Catalog of Nebulae and Star Clusters (NGC2000)” was formed, again, in 1988 by Roger W. Sinnott. This catalogue is a compilation of all known deep sky objects since the first version of the NGC. It has 7840 entries of generally the larger, brighter and more eye-catching objects in the night sky. It includes all astronomers' work, and corrections in errata. Thus, the same object can have different names in different catalogs, such as crab nebula is listed as ‘M1’ in Messier catalogue, whereas ‘NGC1952’ in NGC.
Comments