Apparent size 1.3 by 1.2 arcmin

The second IC lists a corrected RA (per Bigourdan) of 18 10 48. Apparent size 0.5 by 0.3 arcmin.

Apparent size 1.0 on 0.7 arcmin

Located inside the star cloud listed as M24. Apparent size 4.0 arcmin.

Apparent size 6.0 arcmin

Apparent size 29 arcmin

Apparent size 0.9 by 0.7 arcmin

The second IC states "Not found by Howe (3 nights)". Apparent size 0.5 by 0.5 arcmin.

The second IC states "Not found by Howe (2 nights); = 6609?". Apparent size 1.0 by 0.1 arcmin.

In a note about NGC 6608, the second IC states "Not found by Howe (2 nights); = 6609?". Apparent size 0.7 by 0.7 arcmin.

(this entry to contain historical information only; for physical data and images see NGC 6574)

Dreyer's precessed position is a few seconds east and 1.5 arcmin north of the "standard" position, but in comparison to the size of the cluster the discrepancy is minor; so there is no doubt of the identification. Although de Chéseaux discovered the cluster in the 1740's, his only publication of his discoveries was a report to the French Academy of Sciences which was more or less forgotten until Guillaume Bigourdan published a note about de Cheseaux in 1892; so when Dreyer published the New General Catalog, which was primarily an updating and expansion of John Herschel's General Catalog, he credited John Herschel as the discoverer. Why he didn't credit Messier, or John's father William Herschel, is not obvious at this writing. (Far more to follow, but the following is interesting...) The Eagle Nebula and the young star cluster associated with it are about 7000 light years away, meaning we see them as they were 7000 years ago. But up to the left of the brightest part of the nebula, where the star cluster is centered, is a violently expanding cloud of gas caused by a supernova which took place a few thousand years beforehand. Estimates are that six thousand years ago, high-velocity supernova gases slammed into, compressed and simultaneously tore apart the so-called "Pillars of Creation" near the center of the nebula (though we won't see that until a millennium from now). In the process, most of the clouds of gas and dust visible here would be torn apart, but some of the denser nodules hidden inside the Pillars would be violently compressed to quickly form bright new stars. In fact, in such regions close to half the bright stars formed are the result of such events, and for lower mass stars like our Sun, compression by expanding gases is almost always the cause of their formation.

Apparent size 0.7 by 0.7 arcmin

NGC 6613 is a loose collection of about 20 stars, spread over a region about 15 to 20 light-years in diameter, four to six thousand light-years from the Sun (its size being based on its estimated distance, and its apparent size of 7.0 arcmin). Its hottest, brightest members are of the relatively 'early' spectral type B3, which means it is probably about 30 million years old.

Apparent size 1.4 by 1.1 arcmin

Apparent size 1.3 by 0.9 arcmin

The second IC adds (per Howe) "RA is 18 11 47, the 2 stars are 9th to 10th magnitude, one 2 seconds west and 0.6 arcmin south". Apparent size 1.4 by 0.6 arcmin.

Apparent size 1.1 by 0.7 arcmin

Dreyer's precessed position is less than 0.2 arcmin south of the standard position, so the identification is certain. Although de Chéseaux discovered the cluster in the 1740's, his only publication of his discoveries was a report to the French Academy of Sciences which was more or less forgotten until Guillaume Bigourdan published a note about de Cheseaux in 1892; so Messier's discovery was independent. The brighter parts of the nebula appear somewhat like a bird floating on a body of water, hence the "Swan". The brightest part of the nebula extend over 15 light years, but fainter clumps of gas cover 40 or more light years. About three dozen young stars are hidden within the gas and dust of the nebula, which has nearly a thousand solar masses of gas thinly spread over its volume. The Swan is about 5700 light years from the Sun. Apparent size 20 by 15 arcmin.

Apparent size 1.2 by 1.1 arcmin

Apparent size 0.13 arcmin

Based on a recessional velocity of 6190 km/sec, NGC 6621 is about 290 million light years away. However, it is obviously colliding and spectacularly interacting with NGC 6622, whose recessional velocity of 6465 km/sec would suggest a distance of 300 million light years. The two galaxies obviously cannot be at such different distances, so it is probably best to simply say that the pair is about 295 million light years away, give or take a few millions of light years' uncertainty inevitable in even the best such estimates. Given that, NGC 6621's apparent size of 1.7 by 1.0 arcmin corresponds to 145 thousand light years, NGC 6622's apparent size of 0.85 by 0.65 arcmin corresponds to 75 thousand light years, and the overall dimensions of the system (about 2.15 by 1.0 arcmin) correspond to 185 thousand light years.

NGC 6622 is obviously colliding and spectacularly interacting with NGC 6621 (which see for images and a detailed discussion of the system), with which it comprises Arp 81. Note: The galaxy type listed above is based on listings in different databases of types Sbc, Sa, Sab, and the fact that the HST image of the pair shows what appears to be a definite bar in the smaller galaxy. Regardless of what the type chosen should be, there is no question that 'pec' should be added, to take into account the distortion of each galaxy by the other.

Apparent size 1.3 by 1.2 arcmin. Recessional velocity 4845 km/sec. Apparently involved with PGC 61744, which is superimposed on it, and has an essentially identical recessional velocity.

Apparent size 0.15 by 0.15 arcmin. Recessional velocity 4940 km/sec. Apparently involved with NGC 6623, which is superimposed on it, and has an essentially identical recessional velocity. Misidentified in Steinicke as PGC 61749. Although part of a pair with NGC 6623, too faint to have been noticed by Marth, so more likely a companion of, rather than a part of the NGC object.

Apparent size 8.8 arcmin

Apparent size 39 arcmin

Apparent size 1.3 by 1.2 arcmin

Apparent size 1.9 by 1.3 arcmin

Apparent size 0.4 by 0.35 arcmin.

Apparent size 0.8 by 0.7 arcmin

Apparent size 7.0 arcmin

Apparent size 3.0 by 1.4 arcmin

Per Dreyer, NGC 6633 (= John Herschel's GC 4410, Caroline Herschel, 1860 RA 18 20 43, NPD 83 31.3) is a "cluster, a little compressed, large star". Although de Chéseaux discovered the cluster in the 1740's, his only publication of his discoveries was a report to the French Academy of Sciences which was more or less forgotten until Guillaume Bigourdan published a note about de Cheseaux in 1892; so Dreyer had no way of knowing that Caroline Herschel was not the first to see the object. The position precesses to RA 18 27 32.0, Dec +06 33 37, about 3 arcmin northeast of the position listed above, but well within the boundary of the cluster, and "large star" almost certainly refers to 6th-magnitude HD 170200, which is on the southeast periphery of the field; so the identification is certain. The cluster contains a couple of dozen relatively bright stars scattered across an irregularly shaped 20 to 30 arcmin wide field, the brightest being about magnitude 7 1/2. At the cluster's estimated distance of a thousand light years, its apparent size corresponds to about 8 light years. Based on the spectral types of its Main Sequence stars, NGC 6633's age is estimated at six to seven hundred million years.

Per Dreyer, NGC 6634 (= Lacaille list I #11, 1860 RA 18 20 45, NPD 123 30.5) is a "nebula, without stars". The object is now identified as a group of stars without nebulosity, showing the difficulty of determining the nature of faint fuzzy objects with visual observations through a small telescope. (Steinicke notes "not M69". This refers to the fact that Messier was looking for Lacaille's nebula when he found M69, and thought he had rediscovered the same object, as M69 looks nebular in a small telescope; but they are not the same object at all.) The position precesses to RA 18 29 58.2, Dec -33 25 20, about 5 arcmin north of the listed position; but there is nothing else nearby, so the identification is reasonably certain. NGC 6634 consists of less than half a dozen stars ranging from 7th to 9th magnitude, and would have hardly seemed worth mentioning if its true nature had been more readily apparent to Lacaille.

Apparent size 1.0 by 0.9 arcmin

PGC 61782: Apparent size 2.1 by 0.3 arcmin. PGC 61780: Apparent size 0.3 by 0.3 arcmin. PGC 61780 recessional velocity = 4655 km/sec. PGC 61782 recessional velocity = 4393 km/sec. The difference is within the normal range of peculiar (non-Hubble expansion) velocities, so the galaxies are probably a physical pair. PGC 61780 is much smaller and fainter than PGC 61782, so its existence had little if anything to do with Swift's observation; but since it is a physical pair with the larger galaxy, it seems appropriate to list it as part of NGC 6636.

M69 is about 30 thousand light years away. Given that, its 7.1 arcmin apparent size corresponds to about 50 light years. It is said to be one of the most metal-rich of all globular clusters, suggesting a slightly younger age than is typical for such ancient objects; but its stars still have far fewer "metal" atoms (that is, atoms other than hydrogen and helium) than much younger stars like our Sun.

Apparent size 7.3 arcmin

Apparent size 5.0 arcmin

Apparent size 1.1 by 0.8 arcmin

Apparent size 0.9 by 0.7 arcmin

Apparent size 5.8 arcmin

Apparent size 3.7 by 1.8 arcmin

Apparent size 0.2 arcmin

Apparent size 15 arcmin

Apparent size 1.6 by 1.3 arcmin

Per Dreyer, NGC 6649 (= John Herschel's GC 4420, 1860 RA 18 25 44, NPD 100 29.5) is a "cluster, poor, a little compressed, pretty small, stars from 9th-10th and 12th-13th magnitude". Apparent size 6.0 arcmin.