23 3338 24

Ueber die Veranderungen in dem Sternhaufen NGC. 5272. Das Circular Nr. 2, welches soeben von Herrn E. C.

Pickering erhalten wurde,*) veranlasst mich einige Worte meinerseits iiber denselben Gegenstand zu sagen.

Im Jahre 1894 Marz 7 und I I wurde der Sternhaufen Mess. 3 = NGC. 5 2 7 2 (Can. venat. a = 13” 37” d = + 28” 5 5’) am hiesigen photographischen Rohr aufgenommen bei zwei und einer Stunde Exposition. Die Platte vom 7. M L z ist das beste, was ich uberhaupt erhalten konnte. Diese Platte wurde von H. Orbinsky ausgemessen und I 800 Sterne konnlen getrennt werden.

Ich wiederholte die Aufnahmen im Jahre 1895 April I ,

an welchem Tage zwei Aufnahmen gemacht wurden. Diese

zwei Platten sind weit schlechter, als die zwei ersten, aber schon bei fliichtigem Betrachten hat es sich erwiesen, dass in einem der hellsten Sterne (eine Gruppe, welche aus vier dicht aneinander stehenden Sternen besteht) eine rnerkliche Vergrosserung an Helligkeit stattgefunden hat. In I 895 ist der Stern Uber ca. 2 Grossenclassen heller als in 1894. Die vier vorhandenen Platten bestatigen dies ohne jeden Zweifel ; bei naherer, aber sehr fliichtiger Untersuchung des Stern- haufens, da ich selbst gar keine Zeit darauf verwenden kann, fand ich auch noch sofort Unterschiede in der Helligkeit anderer Sterne in den Aufnahmen von 1894 und 1895.

A. Belopolsky. Pulkowo 1895 Noveniber.

*) Vgl. A. N. 3321, E. C. Pickering, Variable star clusters. Kr.

Wells’ Algol Varj -4 minimum of the Algol star, BD. +17?4367, oc-

curred, as predicted in A. N. 3328, on the afternoon of January 5, 1896. Through the courtesy of Professor Young, observations were obtained at Princeton by Professor Taylor Reed, with the 23inch equatorial. It was also observed by Mr. W. M. Reed at Andover. Preparations had been made at this Observatory to obtain a series of photographic images of it automatically, each having an exposure of five minutes, to observe it photometrically with the 1 5 inch equatorial, and also visually with the 1 2 and 6inch equa- torials. Unfortunately, owing to clouds, few observations were obtained, but these serve to show that the star was faint and diminishing in brightness as expected. Similar preparations were made for the next minimum, January 10,

but again clouds prevented observation. The observations so far obtained show that its time

of minimum, uncorrected for the velocity of light, can be closely represented by the formula J. D. z41zooz.500 + 4.8064 E. The uncertainty in the period does not exceed a few seconds, and will probably be known within a single second as soon as the form of light curve is determined.

Harvard College Observatory, I 896 Jan, 3 I

ble in Delphinus. For nearly two hours before and after the minimum it is fainter than the twelfth magnitude. It is impossible, at present, to say how much fainter it becomes or whether it disappears entirely. It increases at first very rapidly and then more slowly, attaining its full brightness, magnitude 9.5, about five hours after the minimum. One hundred and thirty photographs indicate that, during the four days between the successive minima, it does not vary more than a few hundredths of a magnitude. The variation may be explained by assuming that the star revolves around a comparatively dark body and is totally eclipsed by it for two or three hours, the light at minimum, if any, being entirely that of the dark body. The conditions resemble those of U Cephei, which appears to be totally eclipsed by a relatively dark body two and a half magnitudes fainter than itself, but having a diameter at least one half greater. The variation in light of BD. ~ 1 7 0 4 3 6 7 is more rapid than that of any other star hitherto discovered, and as its range is greater than that of any known star of the Algol type, its form of light curve can be determined with corresponding accuracy. U Cephei is second in both these respects.

Edward C. Pickering.

The new star in Centaurus. The Nova (cf. A. N. 3328) follows the nebula NGC.

5 2 5 3 , and is north of it. The nebula is assumed to be Cord. DM. -31010536, magn. 9.5, with which it was ori- ginally identified. As seen with a low power the nebula cannot readily be distinguished from a star. Its magnitude on the Cordoba scale by comparison with adjacent stars was estimated by Mr. Wendell as 9.7, and it could hardly have been overlooked in preparing the Cordoba Durch- musterung, in which many adjacent fainter stars are given. The new star could not have been observed at Cordoba

unless we assume, first, that it was bright at that time, although invariably too faint to be photographed on fifty nights distributed over six years, and secondly, that the nebula was overlooked at Cordoba while observing fainter objects in the same region. Even if we make these as- sumptions, the new star still falls in the same class as T Coronae, which was observed in the northern Durch- musterung several years preceding its appearance as a new star. - The various positions of NGC. 5253 for 1875 are as follows:

2.5 3338 26

Febr. 1 7 1 7 ~ 4m47s

19 ' 1 7 33 18 2 0 I 16 5 2 24

I8 I I 7 2 2 2

RA. Decl. Dreyer's NGC. 1 3h 3Zm5 I f -31OO:z Cordoba DM. 13 32 49.6 -31 0.3 Plate B 13965 13 31 50 .2 -31 o 23" Plate B 14072 13 32 50.0 -31 o 2 1

-1'" 8134 I + 6' 9!'7 2 5 . 5 1 9 ~ 4 5 ~ 4552 1 9 . 6 0 4 ~ : + 5O33'51:'6 I 0,779

+o 17.92 -. 2 44 3 6.3 2 0 9 41.56 1 9 : 6 0 4 ~ ' +13 46 48.6 ' 0.738 -0.38 -12.8 - I 44.97 1 - o 16.5 1 15.3 2 0 24 7.60 I 9.641~1 + I S I I 33.0 0 . 7 5 2

-0i23 -12!7 I I

+ O 46.80 1 + 3 29.7 ~ 25.5 19 56 23.57 9 6 1 3 ~ / + 9 26 33.2 I 0.768 -0.29 -12.9 I 2

l 3 -0.49 -12.4 , 4

Harvard College Observatory, 1896 Jan. 31.

The positions of the Nova derived from these plates differ from each other by only o?r in right ascension and I" in declination. The mean position for 1875 is RA. = 1 3 ~ 3 2 ~ 5 1 f 8 , Decl. =Z -30° 59' 58". It will be noticed that according to these measures, the Nova follows NGC. 5253 by 1f7, and is 24" north.

&'ward C Pickering.

Ueber die rnuthniaassliche Veranderlichkeit eines Sterns nahe x Cygni. Nach vieljahrigen Beobachtungen des Veranderlichen

x Cygni bin ich auf die beiden Sterne 7. Grosse, deren Positionen pro 1800 sind :

A = 295'12' +33" B = 294 40 +32 25'*)

aufmerksam geworden. Der Stern A scheint mir ein wenig veranderlich zu sein, indem er sich bald heller, bald schwacher als der Nachbarstern B zeigt. Aus meinem Beob- achtuogsjournal erlaube ich mir die folgenden Aufzeich- nungen mitzutheilen :

1878 Mlrz 4 A < B April 2 I A > B

1879 Mirz 1 5 A < B 1891 Aug. 30 A < B 1894 Nov. 2 2 A > R

1894 Nov. 30 A > B Dec. 1 2 A < R ' 14 A = B P 16 A < B P 30 A = B

1895 Jan. 1 A > B B 2 1 A = B u 26 A = B

A = R Febr. 10 Nov. 29 A < B Dec. 7 A = B

a 8 A > B ' 14 A = R

Die Schitzungen sind bei ausgeschrobenem Ocular eines astronomischen Fernrohrs von 7 5 mm Oeffnung und bei 42 maliger Vergrosserung ausgefiihrt.

Privatsternwarte, Odder, Danemark, I 896 Jan. 3. Torvald k'iihl.

2.) A ist offenbar RD.+33?3602 6m9, B = BD.+32?3558 6m;. Kr.

Beobachtungen des Cometen 1896 . . . (Perrine-Lamp).

All ' O s s e r v a t o r i o d e l C o l l e g i o R o m a n o d a E. Millosevick.

Febb.18 1 1 7 24 8 I + 3 45.80 1 - 3 42.8 I 9.4 I 19 56 37.94 I 9.6214 + 9 31 2 5 . 0 1 0.733 I -0.30 -13.1 1 5 Equatoriale di om25 di apertura : micrometro filare : ingr. zoo.