Messier 21

Summary

Messier 21 is an open cluster^[1]. It draws 27 Wikipedia views per month (open_cluster category, ranking #21 of 108).^[2]

Key Facts

• Messier 21 is credited with the discovery of Charles Messier^[3].
• Messier 21's image is recorded as Messier object 021.jpg^[4].
• Messier 21's image is recorded as M21a.jpg^[5].
• Messier 21's instance of is recorded as open cluster^[6].
• Messier 21's constellation is recorded as Sagittarius^[7].
• Messier 21's spectral class is recorded as I^[8].
• Messier 21's Commons category is recorded as Messier 21^[9].
• Messier 21's catalog code is recorded as M 21^[10].
• Messier 21's catalog code is recorded as NGC 6531^[11].
• Messier 21's catalog code is recorded as OCl 26.0^[12].
• Messier 21's catalog code is recorded as Collinder 363^[13].
• Messier 21's catalog code is recorded as Melotte 188^[14].
• Messier 21's catalog code is recorded as C 1801-225^[15].
• Messier 21's catalog code is recorded as OCISM 3^[16].
• Messier 21's catalog code is recorded as [KPS2012] MWSC 2796^[17].
• Messier 21's time of discovery or invention is recorded as +1764-06-05T00:00:00Z^[18].
• Messier 21's Freebase ID is recorded as /m/03tkvn^[19].
• Messier 21's topic's main category is recorded as Category:Messier 21^[20].
• Messier 21's Commons gallery is recorded as Messier 21^[21].
• Messier 21's apparent magnitude is recorded as {'amount': '+5.9'}^[22].
• Messier 21's radial velocity is recorded as {'unit': 'Q3674704', 'amount': '-14.7'}^[23].
• Messier 21's distance from Earth is recorded as {'unit': 'Q12129', 'amount': '+1205'}^[24].
• Messier 21's SIMBAD ID is recorded as M 21^[25].
• Messier 21's New General Catalogue ID is recorded as 6531^[26].
• Messier 21's right ascension is recorded as {'unit': 'Q28390', 'amount': '+271.0542'}^[27].

Body

Designation and Status

Messier 21's instance of is recorded as open cluster^[6].

History and Context

Catalog codes include M 21^[10], NGC 6531^[11], OCl 26.0^[12], Collinder 363^[13], Melotte 188^[14], and C 1801-225^[15].

Why It Matters

Messier 21 draws 27 Wikipedia views per month (open_cluster category, ranking #21 of 108).^[2] It has Wikipedia articles in 27 language editions, a strong signal of global cultural recognition.^[28] It is known by 7 alternative names across languages and contexts.^[29]