associated with the Eagle Nebula
|Right Ascension||18 : 18.8 (h:m)
|Declination||-13 : 47 (deg:m)
|Visual Brightness||6.4 (mag)
|Apparent Dimension||7.0 (arc min)
Cluster M16 (NGC 6611) discovered by Philippe Loys de Cheseaux in 1745-6. Nebula IC 4703 discovered by Charles Messier in 1764.
Lying some 7,000 light years distant in the constellation Serpens, and in the next inner spiral arm of the Milky Way galaxy from us, a great cloud of interstellar gas and dust has entered a vivid process of star formation. Open star cluster M16 has formed from this great gaseous and dusty cloud, the diffuse Eagle Nebula IC 4703, which is now caused to shine by emission light, excited by the high-energy radiation of its massive hot, young stars. It is actually still in the process of forming new stars, this formation taking place near the dark "elephant trunks" which are well visible in our photograph, as well as in AAT pictures and other images of M16. A deeper insight in the star formation process could be obtained from the HST images of M16, published in November 1995; moreover, they were used for an animation simulating the approach to this star forming region, and we provide some screen sized images (suitable as backgrounds for your computer screen).
This stellar swarm is only about 5.5 million years old (according to the Sky Catalog 2000 and Götz) with star formation still active in the Eagle Nebula; this results in the presence of very hot young stars of spectral type O6. The cluster was classified as of Trumpler type II,3,m,n (Götz).
Some sources have smaller distances for M16: Kenneth Glyn Jones gives 5,870. Götz 5,540 light years. Götz states that this is one of the intrinsically most luminous open clusters, at an absolute magnitude of -8.21.
While De Cheseaux, in 1745-6, only discovered the cluster, Charles Messier, on his independent rediscovery of June 3, 1764 mentions that these stars appeared "enmeshed in a faint glow", probably suggestions of the nebula. The Herschel's apparently didn't perceive the nebula, so that their catalogs and consequently, the NGC, only describe the cluster. The nebula was added in the IC II of 1908 as IC 4703, with "cluster M16 involved", but the NGC 2000.0 erroneously classifies this object as an open cluster.
Members of the Limber Observatory (Texas) have photographed the same region in M16 as the HST, and display the images side by side at same scale.
Bill Arnett's Eagle Nebula & M16 photo page, info page.
Last Modification: 9 Dec 1999, 22:58 MET