The Eagle Nebula, also known as the Star Queen Nebula, Messier 16 (M16), IC 4703, and NGC 6611, is an emission nebula surrounding a young open star cluster located in Serpens constellation. The nebula is a well-known star forming region. The cluster with which it is associated consists of a number of young stars belonging to the spectral classes O and B.
Messier 16 is best known for the famous Pillars of Creation, a region where intense star forming activity is taking place. The region was imaged by the Hubble Space Telescope in the 1990s. The Eagle Nebula in fact contains several active starburst regions.
The Eagle Nebula was named for its shape, which resembles that of an eagle. It is part of a larger H II region designated as IC 4703, which is a diffuse emission nebula approximately 7,000 light years from Earth.
Messier 16 can be seen in binoculars and amateur telescopes, which reveal about 20 stars and some of the surrounding nebulosity. The three pillars require extremely good observing conditions.
The Eagle Nebula and the open cluster are best observed with low-powered telescopes.
The star cluster associated with the Eagle Nebula was originally discovered by the Swiss astronomer Philippe Loys de Chéseaux in 1745-46. He observed the cluster, but did not see the surrounding nebula.
Charles Messier was the first to discover the nebulosity associated with the open cluster in June 1764.
He noted, “In the same night of June 3 to 4, 1764, I have discovered a cluster of small stars, mixed with a faint light, near the tail of Serpens, at little distance from the parallel of the star Zeta of that constellation: this cluster may have 8 minutes of arc in extension: with a weak refractor, these stars appear in the form of a nebula; but when employing a good instrument one distinguishes these stars, and one remarks in addition a nebulosity which contains three of these stars. I have determined the position of the middle of this cluster; its right ascension was 271d 15′ 3″, and its declination 13d 51′ 44″ south.”
Messier included the nebula in his catalogue as the 16th object on the list, and it remains known as Messier 16.
The nebula was added to the IC II of 1908 as IC 4703, and is often referred to by that designation, while the open cluster is referred to as NGC 6611.
The Eagle Nebula is illuminated by the ultraviolet light of the young stars newly formed in one of the nebula’s star forming regions.
The hot, young stars within the nebula also emit strong X-ray radiation.
The nebula has an estimated mass of more than 12,000 solar masses.
HD 168076, the brightest star in the Eagle Nebula, is a binary system consisting of an O3.5V star and an O7.5V companion. The star system has a visual magnitude of 8.24 and can be seen in good binoculars.
The young open cluster associated with Messier 16 consists of about 460 stars.
The brightest members of the cluster belong to the spectral class O. They are extremely massive, luminous stars, and can be up to a million times brighter than the Sun.
The age of the cluster is believed to be 1-2 million years.
The other name for M16, the Star Queen Nebula, was introduced by the American astronomer Robert Burnham, Jr.
Burnham gave it this name because he thought the central pillar in the nebula looked like the Star Queen shown in silhouette.
The Eagle Nebula was first imaged way back in 1895 by the American astronomer Edward Barnard.
Isaac Roberts photographed it in 1897, after which the object was added to the IC catalogue.
LOCATION AND SIZE
The Eagle Nebula stretches across an area about 70 by 55 light years in size. It lies at a distance of 7,000 light years from Earth. The nebula lies in the Sagittarius-Carina Arm, the inner spiral arm of our galaxy, the Milky Way, next to our own arm.
M16 can be found by first locating the Teapot asterism in Sagittarius constellation, and then by following the line from the star Kaus Australis (Epsilon Sagittarii), the brightest star in Sagittarius, to just east of Kaus Media (Delta Sagittarii). Another way to find the nebula is by extending a line from Lambda Scuti in Scutum constellation to Alpha Scuti, and then to the south to Gamma Scuti.
In good viewing conditions, the open cluster in M16 is easy to find, but to see the surrounding nebulosity well, one needs a large aperture telescope.
The best time to observe the Eagle Nebula from the northern hemisphere is summer and early autumn, when the nebula can be found in the southern sky in the evening.
Eagle Nebula – Messier 16 (NGC 6611)
Constellation: Serpens Cauda
Coordinates: 18h18m48s (right ascension), -13°49′ (declination)
Distance: 7,000 light years
Visual magnitude: +6.0
Absolute magnitude: -8.21
Apparent dimensions: 7.0 arc minutes
Radius: 70×55 light years
Estimated age: 5.5 million years
Designations: Eagle Nebula, Star Queen Nebula, Messier 16 (M16), NGC 6611, IC 4703, Gum 83, Sharpless 49, RCW 165
PILLARS OF CREATION
The region known as the Pillars of Creation became famous in 1995, when it was imaged by Jeff Hester and Paul Scowen using the Hubble Space Telescope. It is one of the star forming regions within the Eagle Nebula. The pillars stretch across an area of approximately four light years and are illuminated by the light of newly formed stars.
The pillars region is similar to the larger Soul Nebula, located in Cassiopeia constellation, which was nicknamed the Pillars of Star Formation.
The region consists of columns of interstellar dust and hydrogen gas within which new stars are formed. The dense pockets of gas seen at the top of the pillars are called EGGs, or evaporating gaseous globules, and last for about 10,000-20,000 years. Those that contain enough gas will eventually collapse to form new stars.
Images obtained from the Spitzer Space Telescope in 2007 indicate that the pillars may have been destroyed as a result of a supernova explosion in the vicinity, but the light showing the result of the supernova will not reach us for another 1,000 years.
The supernova event is believed to have occurred about 8,000 to 9,000 years ago. The shock wave from the explosion would have taken a few millennia to move through the region, and the nebula is 7,000 light years distant from Earth, which means that we are seeing it as it appeared 7,000 years ago. The area where the supernova exploded is full of young, very massive stars that are also ready to explode.