Discovered: 1654 by the Italian astronomer Giovanni Battista Hodierna [1], Observed and cataloged on May 23, 1764 by Charles Messier. [2]

Object Type: Emission Nebula [1]

Apparent Magnitude: 6.0 [1]

Distance: 5,200 light-years away [1]

Other Designations: NGC 6523, SH2-25, LBN 25, RCW 146, GUM 72 [3]

Constellation: Sagittarius [1]

Notes from Messier:

May 23, 1764. 5. 15h 06m 36s (226d 39' 04") +2d 57' 16"
Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens], near the star in the Serpent, of 6th magnitude, which is the 5th according to the Catalog of Flamsteed [5 Ser]: it doesn't contain any star; it is round, & one sees it very well, in a fine [clear dark] sky, with an ordinary refractor of 1-foot [FL]. M. Messier has reported it in the chart of the comet of 1763. Mem. Acad for the year 1774, page 40. Reviewed on Sep. 5, 1780, January 30 & March 22, 1781. (Diam. 3') [2]

[Mem. Acad. for 1771, p. 437 (first Messier catalog)]
The night of May 23 to 24, 1764, I have discovered a beautiful nebula in the constellation of Serpens, near the star of sixth magnitude; the fifth according to the catalog of Flamsteed. That nebula doesn't contain any star; it is round, & could have a diameter of 3 arc minutes; one can see it very well, under a good sky, with an ordinary [non-achromatic] refractor of one foot [FL]. I have observed that nebula in the Meridian, & I have compared it to the star Alpha Serpentis. Its position was right ascansion 226d 39' 4", & its declination 2d 57' 16" north. On March 11, 1769, at about four o'clock in the morning, I have reviewed that nebula with a good Gregorian telescope of 30 pouces, which magnified 104 times, & I have ensured that it doesn't contain any star. [2]