Tag Archives: M21

M8, M20, M21, NGC 6559


All four objects on this awesome image are located in Sagittarius:

– The Lagoon Nebula (catalogued as Messier 8 or M8, and as NGC 6523) is a giant interstellar cloud. It is classified as an emission nebula and as a H II region. The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and is one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. Seen with binoculars, it appears as a distinct oval cloudlike patch with a definite core. A fragile star cluster appears superimposed on it.

– The Trifid Nebula (catalogued as Messier 20 or M20 and as NGC 6514) is an H II region. It was discovered by Charles Messier on June 5, 1764. Its name means ‘divided into three lobes’. The object is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent ‘gaps’ within the emission nebula that cause the trifurcated appearance; these are also designated Barnard 85). Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.

– Messier 21 or M21 (also designated NGC 6531) is an open cluster of stars. It was discovered and catalogued by Charles Messier on June 5, 1764. M21 is a relatively young cluster of a mere 4.6 million years of age. It is tightly packed but contains about 57 stars. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night.

NGC 6559 is a star forming region located at a distance of about 5000 light-years from Earth, showing both emission (red) and reflection (bluish) regions.

Imaging telescopes or lenses: Pentax 75 SDHF
Mounts: Losmandy G11 Gemini 3
Software: Pleiades Astrophoto, S.L. PixInsinght 1.8 RC7
Filters: Baader Planetarium SII 8nm,  Baader Planetarium Ha 7nm ,  Baader Planetarium OIII 8.5nm 2″
Resolution: 3987×2650
Dates: June 21, 2014,  July 22, 2014,  July 23, 2014
Baader Planetarium Ha 7nm : 18×900″ bin 1×1
Baader Planetarium OIII 8.5nm 2″: 13×900″ bin 2×2
Baader Planetarium SII 8nm: 9×900″ bin 2×2
Integration: 10.0 hours
Avg. Moon age: 24.78 days
Avg. Moon phase: 24.09%
Locations: La Secuita, La Secuita, Spain
Author: Daniel_Trueba

Messier 20 and 21 

Image Credit & Copyright: Lorand Fenyes

 The beautiful Trifid Nebula, also known as Messier 20, is easy to find with a small telescope in the nebula rich constellation Sagittarius. About 5,000 light-years away, the colorful study in cosmic contrastsshares this well-composed, nearly 1 degree wide field with open star cluster Messier 21 (top right). Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20’s, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21’s stars are much older, about 8 million years old.

APOD NASA 28-Aug-14