| Hubbleminus Strassburg | |||
|---|---|---|---|
| N.G.C. | Δα | Δδ | |
| 379 | 0ˢ.0 | + 3 | ″ |
| 380 | +0.1 | + 3 | |
| 382 | +0.2 | + 1 | |
| 383 | +0.1 | 0 | |
| 384 | +0.1 | + 1 | |
| 385 | +0.1 | + 2 | |
| 386 | -0.2 | - 2 | |
| 387 | +0.2 | + 3 | |
| 3550[2] | +0.5 | +24 | |
| 3552 | +0.1 | +19 | |
| 3554 | -0.2 | +15 | |
| 3558 | -0.3 | - 1 | |
| 6329 | -0.3 | + 3 | |
| 6332 | -0.3 | + 6 | |
| 6336 | +0.1 | + 8 | |
| 7586 | +0.2 | + 1 | |
| 7608 | -0.3 | + 6 | |
| 7611 | -0.2 | - 1 | |
| 7612[3] | 0.0 | + 2 | |
| 7617 | +0.1 | + 1 | |
| 7619[4] | +0.1 | - 1 | |
| 7623[5] | 0.0 | + 1 | |
| 7626[6] | -0.2 | - 2 | |
TABLE III
Distribution of Varieties or Classes of
Nebulae in the Seven Clusters or Fields
| Class | Field | |||||||
|---|---|---|---|---|---|---|---|---|
| I | II | III | IV | V | VI | VII | Total | |
| a | 1 | 1 | ||||||
| c | 1 | 1 | 1 | 3 | ||||
| d | 1 | 33 | 1 | 6 | 41 | |||
| e | 27 | 39 | 109 | 41 | 27 | 21 | 20 | 284 |
| f | 33 | 35 | 17 | 19 | 8 | 12 | 21 | 145 |
| g | 7 | 3 | 4 | 12 | 5 | 7 | 38 | |
| g₀ | 5 | 8 | 3 | 1 | 17 | |||
| h | 2 | 2 | 2 | 10 | 1 | 1 | 4 | 22 |
| h₀ | 3 | 2 | 4 | 1 | 2 | 2 | 14 | |
| i | 1 | 2 | 3 | |||||
| k | 1 | 2 | 3 | |||||
| n | 1 | 1 | ||||||
| q | 1 | 2 | 3 | |||||
| r | 2 | 2 | ||||||
| v | 1 | 1 | ||||||
| w | 1 | 4 | 2 | 7 | ||||
| irreg | 1 | 2 | 3 | |||||
Messier 60 has a spiral as a very near neighbor—H III 44. The contrast in the two classes is well shown; so also in the case of N.G.C. 3379 mentioned above. Here there is a group of three fairly bright nebulae: N.G.C. 3379, a globular nebula of class e; 3389, an open spiral; and 3384, which might be called a spindle, except that the wings flare out from the nucleus.
The three irregular forms are N.G.C. nebulae and are commented upon in the descriptions accompanying the positions.
Very little can be said concerning the surface-brightness of these objects. It is independent of the distance so long as the angular diameter is sensibly greater than that of a faint star. The photographic plate therefore records the absolute surface-brightness of the nebulae. High luminosity is a comparatively rare attribute and there is some relation between luminosity and absolute size; that is to say, the brighter usually have the greater angular diameter. Since it is hard to conceive of a relation between distance and absolute brightness, the fact that the faint nebulae are usually the smaller can be interpreted only in the light of a relation between luminosity and absolute size.
The clustering of the nebulae here recorded is very pronounced. In the center of Field III there are some 75 nebulae scattered over an area equal to that subtended by the full moon.[7] In order to examine the distribution of the different sizes, diameters were plotted against frequencies. The small scale of the plates renders the number of smallest diameters very uncertain. Nebulae less than 10″ in diameter might easily be mistaken for stars and overlooked, especially if they are at some distance from the center of the field. The curves resemble probability-curves, as one would expect for random distribution in a cluster at a definite distance.
TABLE IV
Distribution According to Size
of the Nebulae in Three Fields