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N.G.C. 1722. a = 4h 52m6; 8 = —69° 33'; A = 326° 52'; p = —83° 4' The nebula is hive-shaped, about 15" in length and 7" in width at widest point, with stellar nucleus near south following end. A 10.5 magnitude star is 30" n. p. the nebula. This nebula is situated in the Greater Magellanic Cloud. The exposures were made upon the nucleus.
:4h 56m6; 8 = —66° 34'; A = 352° 33' This object is an extended combination of stars and nebulosity about I15 long, situated in the Greater Magellanic Cloud. H/3 seems as bright as N,.
N.G.C., 2115. a = 4h 56m8; 8 = —66° 32'; A = 352° 52'; /3 = —83° 44' Small round planetary, about 6" in diameter and about 10.5 magnitude. A 10th magnitude star is 50" north preceding. It is in the Greater Magellanic Cloud.
N.G.C2 2116. a = 4" 57m3; 8 = —66° 33' Nebulous patch, 10" in diameter, limits indefinite; less than 11th magnitude. A 10th magnitude star lies about 40" south of the nebula. Wilson saw one bright line in its spectrum, too faint to photograph. The bright-line character of the spectrum was observed by Mrs. Fleming in 1901; Harvard Circular, No. 60.
N.G.C., 2117. a = 4h 57m5; 8 = —68° 35' Faint patch about 10" in length and not over 5" in width at widest point. Is on the following edge of a cluster. Bright lines seen in its spectrum; possible to photograph the lines, but guiding would be difficult. The bright-line character of the spectrum was observed by Mrs. Fleming in 1901; Harvard Circular, No. 60.
Jonckheere 320. a = 5h 0m0; 8 = +10° 34'; A = 74° 55'; /3 = —12° 6' Dr. Curtis's photograph of this fairly bright nebula, discovered by Jonckheere in 1916, was available for our guidance before we began to observe it, and we accordingly obtained its radial velocity from the spectrograms taken to test for rotation, as below.
The first two spectrograms were obtained with the slit along the major axis of the bright oval disk (about 8" X 5"), and they show very marked inclination of the N, and N„ lines. With the slit placed on the short axis of figure (October 27, 1916) the nebular lines show no perceptible inclination, while on the last plate taken with the slit along the major axis of the faint outer ring the lines are inclined, but by a smaller amount than on the first two plates. The spectrum of the faint ring was not recorded.
In the following table are given the data for the observed inclination of the lines from the measures of Messrs. Campbell and Moore, expressed as relative velocities northwest — southeast and north — south for the two positions of the slit. Two methods of measurement, indicated in the table under a and b, were employed: a, in which the angle of inclination of the nebular line was measured; b, by direct settings in the usual manner with the micrometer wire placed parallel to the direction of the comparison lines. In the case of short lines the second method will in general give the smaller values of the inclination. Slit along the major axis of bright oval, pa = 118°.
Our results indicate that this nebula is in rapid rotation about an axis coinciding approximately with the shorter axis of the bright central oval, in the sense that a point on the major axis of the oval 3 seconds of arc northwest of the center has a velocity of recession of about 13 km./sec. relative to that of the corresponding point southeast of the center.
N.G.C. 1935. a = 5h 22m2; 8 = —68° 3'; A = 333° 18'; p = —86° 4' A triangular-shaped nebula with lane running through one corner; 15" on each edge; has three apparently stellar nuclei, two brighter of which are in the larger (north) part of the nebula. The nebula is situated in the Greater Magellanic Cloud.
Fig. 13—Finder field (Wilson) for:
1, N.G.C. 1935 3, N.G.C. 1949
2, N.G.C. 1936
Fig. 14—Drawing of N.G.C. 1935 (Wilson).
N.G.C. 1936. a = 5h 22*5; 8 = —68° 4'; A = 332° 59'; |3 = — 86° 5' Round, planetary, about 15" in diameter; limits indefinite; trace of nucleus near north edge. In same field with N.G.C. 1935, and like this is in the Greater Magellanic Cloud.
N.G.C, 418. a = 5" 22*9; 8 = —12° 46'; \ = 78° 49'; /S = —35° 52' The peculiarities in the spectrum of this nebula were described by Campbell in Astron. and Astro-Phys., 13, 494, 1894. The diameters of the N„ N,, and H/3 images were then estimated to be 11", 8", and 14" respectively, and their relative visual intensities as 10:3:7. On the spectrograms the H/3 line is much stronger than N,.
The last three plates, exposed for rotation tests, show no certain inclination of the lines. Plate XXVII, figure 15, is a direct reproduction of the 3-prism 32-inch spectrogram secured on November 16, 1916.
N.G.C. 1949. a = 5h 25*6; 8 = —68° 33'; A = 324° 42'; / 3 = —86° 10' A faint planetary nebula, slightly elongated, about 8" X 10", uniformly brighter towards center, and situated in the Greater Magellanic Cloud.
N.G.C. 1952. a = 5h 28m5; 8 = +21° 57' This is the "Crab" nebula. Winlock at Harvard Observatory observed its spectrum, in 1869, to contain bright lines. Dr. Slipher reports, in Nature, 95, 185, 1915, that Nlf N„, H/3, N,, and Hy are present on a plate exposed 18 hours with a very efficient spectrograph. Each line is double, with maximum separation of the components 40A, but the separation varies in different parts of the nebula. We have no quantitative observations, asv the spectrum is unpromising for radial velocity determinations; but Mr. Moore verified, visually, the presence of bright lines, exceedingly faint.