"M16 (NGC 6611): The Eagle Nebula (I)" (II) Messier Objects MIV: Our Milky Way Galaxy MWG (i) MWG (ii)
Beryllium in turnoff stars of NGC 6397 Eagle (giant molecular cloud) M16 (ISO) 2MASS (HII) Messier Catalog Five Years of VLT The November 1995 Hubble shots of M16 Hubble's 15th Anniversary: M51 & M16 Animationen: HST K1 Adlernebel M16: Info VLT K2 M16: Nebula With Star Cluster K3 M16: Stars from Eagle's EGGs K4 M16 — Star Birth in the Nest of the Eagle K5 Molecular excitation in the fingers	— :    Adlernebel M16 Literatur

M16: The Eagle Nebula (NGC 6611)

Image credit: NASA, ESA, STScI, J. Hester and P. Scowen FIG. 2.— Star-Birth Clouds in M16: Stellar "Eggs" Emerge from Molecular Cloud

K1  Adlernebel M16: Info

Der Adlernebel trägt im Messier-Katalog die Bezeichnung M 16 bzw. im NGC die Nummer 6611. Er befindet sich im Sternbild Schlange an den Koordinaten 18h19m (Rektaszension) und 13,47° (Deklination).
Seine Entfernung zur Sonne beträgt etwa 2 kpc. Er weist eine scheinbare Helligkeit von 6,4^m auf.

1995 machte das Hubble-Weltraumteleskop Aufnahmen dieser Region und offenbarte faszinierende Strukturen. Der Nebel enthält Staubsäulen die etwa ein Lichtjahr lang sind und an deren Spitze sich neue Sterne befinden, weshalb sie auch "Pillars of Creation" (Säulen der Schöpfung) getauft wurden. Jüngste Analysen im Infrarotbereich lassen diese Theorie allerdings wanken. Es wäre möglich, das der Nebel vom Staub ehemaliger Sterne herrührt.

Eagle Nebula Kategorie: Astronomischer Nebel (H II Region)

K1.1  The Eagle's EGGs

Young Stars in the Famous "Pillars of Creation"
Image credit: ESO / VLT FIG. 2.— Dunkles Herz: Infrarotbild von den Innereien des Adlernebels		Ref.: Beryllium in turnoff stars of NGC 6397 (Pasquini, et al. A&A 426 (2004)) Messier 16 (M16), also known as the Eagle Nebula, is located in the southern constellation of Serpens. Using the infrared multi-mode ISAAC instrument on the 8.2-m VLT ANTU telescope, European astronomers were able to image the Eagle Nebula at near-infrared wavelength. The ISAAC near-infrared images cover a 9 x 9 arcmin region, in three broad-band colours and with sufficient sensitivity to detect young stars of all masses and - most importantly - with an image sharpness as good as 0.35 arcsec. The wide-field view of M16 shows that there is much happening in the region. The first impression one gets is of an enormous number of stars. Those which are blue in the infrared image are either members of the young NGC 6611 cluster - whose massive stars are concentrated in the upper right (north west) part of the field - or foreground stars which happen to lie along the line of sight towards M16. Most of the stars are fainter and more yellow. They are ordinary stars behind M16, along the line of sight through the galactic bulge, and are seen through the molecular clouds out of which NGC 6611 formed. Some very red stars are also seen: these are either very young and embedded in gas and dust clouds, or just brighter stars in the background shining through them.
Three-colour composite mosaic image of the Eagle Nebula (Messier 16), based on 144 individual images obtained with the infrared multi-mode instrument ISAAC on the ESO Very Large Telescope (VLT) at the Paranal Observatory. At the centre, the so-called "Pillars of Creation" can be seen. This wide-field infrared image shows not only the central three pillars but also several others in the same star-forming region, as well as a huge number of stars in front of, in, or behind the Eagle Nebula. The cluster of bright blue stars to the upper right is NGC 6611, home to the massive and hot stars that illuminate the pillars.

HH 216 in M16 — CO (J=2-1) spectra — CS (J=2-1) and C18O (J=2-1) lines
	Authors: M. Andersen, J. Knude, B. Reipurth, A. Castets, L. Å. Nyman, M. J. McCaughrean, and S. Heathcote
	Journal-ref: A&A 414 (2004) 969–978 [ ]
	Title: Molecular cloud structure and star formation near HH 216 in M16
Abstract: We present millimetre, optical, and near-infrared observations of M 16 in the vicinity of the Herbig-Haro object HH 216. The line profiles of the CO (J=2-1) spectra are broad and consist of both emission originating from four warm molecular cores and a large cloud or cloud system across the whole field. The CS (J=2-1) and the C18O (J=2-1) lines are relatively broad compared with those observed in low-mass star formation regions, but not unusually broad for higher-mass star-forming regions. The virial masses found are much larger than the mass estimates based on the assumption of LTE. The optiimages suggest that HH 216 is the terminating bow shock of a large Herbig-Haro flow which includes a jet. A possible location for the driving source is suggested, from the presence of a very reddened point source associated with what may be a small reflection nebula at the tip of a dense molecular ``trunk''. Another reflection nebula associated with the same core is also detected. This demonstrates that star formation is taking place in the trunk.

Credit: Anglo-Australian Telescope photograph by David Malin Copyright: Anglo-Australian Telescope Board  January 18, 1997

The gorgeous spectacle lies toward the galactic center region, some 7,000 light years distant in the constellation Serpens. Most of the stars in the cluster can be seen offset just above and to the right of the photograph's center.

This type of star cluster is called an "open" or "galactic" cluster and typically has a few hundred young bright members. The redness of the surrounding emission nebula gas is caused by electrons recombining with hydrogen nuclei, while the dark regions are dust lanes that absorb light from background sources. The dust absorbs so much light it allows astronomers to determine which stars are inside the nebula and which are in the foreground.

Stars are forming within the nebula, also known as the Eagle Nebula.

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	Authors: Hester, J. J.; Scowen, P. A.; Sankrit, R.; Lauer, T. R.; Ajhar, E. A.; Baum, W. A.; Code, A.; Currie, D. G.; Danielson, G. E.; Ewald, S. P.; Faber, S. M.; Grillmair, C. J.; Groth, E. J.; Holtzman, J. A.; Hunter, D. A.; Kristian, J.; Light, R. M.; Lynds, C. R.; Monet, D. G.; O'Neil, E. J., Jr.; Shaya, E. J.; Seidelmann, K. P.; Westphal, J. A.
	Journal-ref: AJ 111 (1996) 2349 [ ]
	Title: Hubble Space Telescope WFPC2 Imaging of M16: Photoevaporation and Emerging Young Stellar Objects
The Hubble Space Telescope team consisted of Jeff Hester and Paul Scowen and 21 collaborators. Their M16 image was made at visible wavelengths using the Wide-Field Planetary Camera 2 (WFPC-2) instrument of the HST, selecting the emission lines of double ionised oxygen [OIII], the hydrogen line H-alpha, and single ionised sulphur [SII] in the visible wavelength interval (from 500 to 671 nm). The image was released by the Space Telescope Science Institute (PR95-44) in 1995 and the scientific data analysis was published by Jeff Hester et al. in the Astronomical Journal in 1996 (Vol. 111, p. 2349).

"Säulen der Schöpfung" im Adlernebel: Kühles Gas und Staub.
Image credit: J. Hester, P. Scowen, HST, NASA FIG. 3.— M16: Stars from Eagle's EGGs		[2000 September 24] Explanation: Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars' end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away.

solar system — formation in a region like the Eagle nebula
	Authors: Hester, J. Jeff; Desch, Steven J.; Healy, Kevin R.; Leshin, Laurie A.
	Journal-ref: Science 304 (2004) 1116-1117 [ ]
	Title: The Cradle of the Solar System
Abstract: The recent discovery of decay products of 60Fe in meteorites challenges conventional wisdom about the environment in which the Sun and planets formed. Rather than a region like the well-studied Taurus-Auriga molecular cloud, the solar system must have formed instead in a region more like the Eagle nebula — a region that contained one or more massive stars that went supernova, injecting newly synthesized radionuclides into the nascent solar system. In their Perspective, Hester et al. discuss a scenario by which the solar system — and other low-mass stars like the Sun — could have formed. Radiant energy from massive, luminous stars first compresses surrounding interstellar gas, triggering the formation of Sun-like stars, then quickly disperses this material, exposing newborn stars and their protoplanetary disks to harsh radiation from the massive stars. When the massive stars go supernova, they pelt surrounding protoplanetary disks with ejecta laden with the products of stellar nucleosynthesis that are required to explain the isotopic composition we see today.

ven as, over the past decade, astronomers and astrophysicists have peered ever deeper into the processes of star formation, the World Wide Web has evolved into a medium of extraordinary power for disseminating astronomical information to specialists — and for making the vast realm of the stars accessible to the general public.

On a clear, dark summer night earth-based observers can see these glowing clouds, called nebulae, scattered along the track of the Milky Way. Many can be found by looking in the direction of the great star clouds in the summer constellation, Sagittarius.

One of the most unique star-birth regions is the Eagle Nebula, (also called M16 because it is in the Messier Catalog of "fuzzy" permanent objects in the sky, that was compiled more than 200 years ago by French astronomer Charles Messier) it is visible in binoculars near the border between the constellations of Sagittarius and Serpens. The nebula is actually a bowl-shaped blister on the side of a dense cloud of cold interstellar gas.

Most of this cloud is so dense and cool that its hydrogen atoms are bound as molecules. This "molecular hydrogen" is the raw material for building new stars. The cloud contains microscopic dust particles of carbon (in the form of graphite), silicates and other compounds similar to those found in terrestrial and lunar rocks. Though this trace dust accounts for only a fraction of the nebula's mass, it's enough dust to absorb visible light — cloaking some of the visual details of star birth.

A cluster of about 100 newborn stars glitters inside the open "bowl" of the nebula. A few of these stars are much more massive than our Sun is, and so are tremendously hotter and brighter than the Sun. The brightest of these stars may be 100,000 times brighter than the Sun and have temperatures of nearly 90,000 degrees Fahrenheit (50,000 degrees Kelvin).

These young stars emit intense ultraviolet radiation which is so energetic it heats the surrounding gas, causing it to glow like the gas inside a fluorescent light bulb. When this ultraviolet light hits the bowl-shaped surface of the molecular cloud, it heats that gas, causing it to "evaporate" and stream away from the surface. If one could watch the process for more than a million years, they would see the bowl grow increasingly larger as the radiation from the stars eats deeper into the molecular cloud.

Unlike other stellar nebula which we see face-on — like the great Orion Nebula — M16 presents astronomers with a unique side view of the structure of a typical star-birth region: the cluster of hot, young stars in the center of the cavity, the evaporating surface of the cloud, and finally the great cold mass of the cloud itself. The Eagle Nebula's name comes from its symmetrical appearance which is reminiscent of a bird of prey with outstretched wings and talons bared. The Eagle's "talons" are actually a series of dense columns of gas that protrude into the interior of the nebula. These columns form as a result of the same process that causes the bowl to grow. Because the columns are denser than their surroundings, they are not evaporating as rapidly as the surrounding gas, and so remain. The process is analogous to the formation of towering buttes and spires in the deserts of the American Southwest. These geological features formed when wind and rain eroded away softer ground, but places where the rock was harder resisted erosion and were left behind.

		Eagle EGGs in M16 [February 28, 1998] Explanation: Star forming regions known as "EGGs" are uncovered at the end of this giant pillar of gas and dust in the Eagle Nebula (M16). EGGs, short for evaporating gaseous globules, are dense regions of mostly molecular hydrogen gas that fragment and gravitationally collapse to form stars. Light from the hottest and brightest of these new stars heats the end of the pillar and causes further evaporation of gas - revealing yet more EGGs and more young stars. This picture was taken by the Wide Field and Planetary Camera on board the Hubble Space Telescope. credit: J. Hester & P. Scowen (ASU), HST, NASA

Inside these interstellar columns, the gas density can get so high that gravity takes over and causes the gas to start collapsing into ever-smaller clumps. As more and more gas falls onto these growing clumps they get further compressed by their own weight, until finally they trigger nuclear fusion reactions in their cores, and "turn on" as stars.

However, in M16 this process may not get a chance to go on to completion. If a forming star and the gas cloud that surrounds it are "uncovered" by photoevaporation before the star finishes growing, the mass of the young star may be "frozen." The star can't grow any more simply because the cloud from which it was drawing material is gone. In M16 Hubble Space Telescope's high resolution seems to have caught about 50 stars in this situation.

These are called EGGs "evaporating gaseous globules." The acronym is appropriate because these EGGs are objects within which stars are being born and are now emerging.

M16 is where the action is today, but it won't remain so forever. Within another few million years, star formation will have exhausted or dispersed the available raw material, and the massive stars that illuminate the Eagle will have lived out their short lives and died in spectacular supernova explosions. But even though the "birth cloud" nebula will be gone, most of the stars that formed there will remain. The offspring of the Eagle will "take wing" among the rest of the hundreds of billions of stars that make up our galaxy.

K5   Molecular excitation in the fingers

M16 (Eagle) nebula — d = 1.8 ± 0.5 kpc — age: 1.3 ± 0.3 Myr
	Authors: F. Schuller, S. Leurini, C. Hieret, K. M. Menten, S. D. Philipp, R. Guesten, P. Schilke, L.-A. Nyman
	Journal-ref: A&A 454 (2006) L87 [astro-ph/0606155 ]
	Title: Molecular excitation in the Eagle nebula’s fingers
Abstract: The M16 nebula is a relatively nearby Hii region, powered by O stars from the open cluster NGC 6611, which borders to a Giant Molecular Cloud. Radiation from these hot stars has sculpted columns of dense obscuring material on a few arcmin scales. The interface between these pillars and the hot ionised medium provides a textbook example of a Photodissociation Region (PDR). Aims: To constrain the physical conditions of the atomic and molecular material with submillimeter spectroscopic observations. Methods: We used the APEX submillimeter telescope to map a ~3'x3' region in the CO J=3-2, 4-3 and 7-6 rotational lines, and a subregion in atomic carbon lines. We also observed C18O(3-2) and CO(7-6) with longer integrations on five peaks found in the CO(3-2) map. The large scale structure of the pillars is derived from the molecular lines' emission distribution. We estimate the magnitude of the velocity gradient at the tips of the pillars and use LVG modelling to constrain their densities and temperatures. Excitation temperatures and carbon column densities are derived from the atomic carbon lines. Results: The atomic carbon lines are optically thin and excitation temperatures are of order 60 K to 100 K, well consistent with observations of other Hii region-molecular cloud interfaces. We derive somewhat lower temperatures from the CO line ratios, of order 40 K. The Ci/CO ratio is around 0.1 at the fingers tips. 1. Introduction The interplay of massive stars with their surrounding interstellar medium, though of critical importance in the energy budget of a galaxy, is still poorly understood due to observational limitations, and to the generally large distance to high mass star forming regions. Located only 1.8 ± 0.5 kpc away, the M16 (Eagle) nebula is one of the best templates for detailed analysis of the environment of high-mass stars. This nebula is associated with the NGC 6611 star cluster, which contains more than two dozen stars of spectral type earlier than B0 and hundreds of lower mass stars and has an age of 1.3 ± 0.3 Myr. To the south of this cluster, the radiation from these hot stars has sculpted columns of dense obscuring material on a few arcmin scales, usually referred to as ’fingers’ or ’pillars’, of which Hester et al. (1996) presented stunning Hubble Space Telescope (HST) images. The boundary between the HII region and the dense molecular gas provides an archetype of a Photodissociation Region (PDR). Indications of present-day star formation near the tips of the fingers are seen e.g. at infrared (IR) wavelengths. The fingers have been mapped in the J = 1 - 0 line of CO and isotopologues by Pound (1998) with the BIMA array. White et al. (1999) used the JCMT 15 m and OSO 20 m radiotelescopes to map the same region in various molecular lines and in the submm continuum. They report CO(2–1) and CO(3–2) peak brightness temperatures above 40 K and 60 K, respectively, and a factor 2–3 lower temperature in CO(1–0).

Literatur zu "M16 (I)"
Hester, J. J.; Scowen, P. A.; Sankrit et al.	1996	AJ 111, 2349	"HST Imaging of M16: Photoevaporation and Emerging Young Stellar Objects"
M. Andersen, J. Knude, B. Reipurth, et al.	2004	A&A 414, 969–978	"Molecular cloud structure and star formation near HH 216 in M16"
Hester, J.J.; Desch, S.J.; Healy, K.R.; Leshin, L.A.	2004	Science 304, 1116-7	"The Cradle of the Solar System"
F. Schuller, S. Leurini, et al.	2006	A&A 454, L87	"Molecular excitation in the Eagle nebula’s fingers"

H. Heintzmann

( Eintrag vom 14.7.2007)

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