Page images
PDF
EPUB

been photographed several times by Gould at Cordoba; and Dr. Gould also reports that he has eight plates of Eta Argús and surrounding stars, of which a very large number is secured upon the photograph by an exposure of from eight to ten minutes.

Dr. Valentiner, at Mannheim, has begun the investigation of several star clusters, and such investigations are to be continued as a principal work of this observatory.

At Kiel, Peters continues observations of nebulæ for position, which were undertaken at Altona.

Dr. Schmidt, of Athens, has just published in the Astronomische Nachrichten a suggestive paper on the connection of the nebula h. 3770 with variable stars in the vicinity. His facts seem to indicate a relation between them.

M. Tempel, of Florence, sends to the Astronomische Nachrichten, No. 2138, a long account of his observations of nebulæ at Florence, which are prosecuted under many difficulties, and gives some account of the great variations which he has found to exist between drawings of the same nebula by various observers.

Professor Holden has a paper in Silliman's Journal on the proper motion of the Trifid Nebula.

From the older observations of the two Herschels it fol. lows that

1. From 1784, July 12, to 1833, the triple star Sh. 379 2008 centrally situated between the three nebulosities.

Again, from the later observations of Mason, Herschel, Lassell, Langley, Trouvelot, and Holden, it follows that

2. From 1839 to 1877 the triple star was not centrally situated between the three nebulosities, but involved in A.

It is shown that each of these propositions rests on a firm basis. Granted that 1 and 2 are correct, there are but three ways to reconcile the opposing facts:

a. The triple star has a large proper motion. 6. The nebula has a large proper motion. c. The nebula is subject to decided changes of brilliancy.

The first point will be settled by meridian observations now in progress. The relative positions of the various stars of the group seem to have been unchanged since 1839. If, as is probable, the proper motion of the triple star is small, there remain the two alternatives b and c to choose between. Mr. Plummer has a note on the collective light distribution of the fixed stars. He finds that fully three fourths of the light of a fine night comes from stars which are individually invisible to the naked eye, and that on his hypothesis the total light of all the stars of the Durchmusterung is equal to 10.17 Venus at maximum brilliancy, or 1: 78.6 of the mean full moon. His final conclusion is that “either the Durchmusterung contains many stars (more than one third of the entire number) which, though rated as 9.5 magnitude, are sensibly below it, or else it must be assumed that at the average distance for stars of this magnitude a denser stratum actually exists, succeeded possibly by regions less fruitful beyond."

NEW STARS. “Schmidt's observations of the new star of 1866 (T Corono), continued up to the present time, show that after falling from the second to the seventh magnitude in nine days, its light diminished very gradually year after year down to nearly the tenth magnitude, at which it has remained pretty constant for the last two years. But during the whole period there have been fluctuations of brightness at tolerably regular intervals of ninety-four days, though of successively decreasing extent. After the first sudden fall, there seems to have been an increase of brilliancy which brought the star above the seventh magnitude again, in October, 1866, an increase of a full magnitude; but since that time the changes have been much smaller, and are now but little more than a tenth of a magnitude. The color of the star has shown no. change from pale yellow throughout the whole course of observations.”

Lord Lindsay makes the important announcement that Schmidt's Nova Cygni (R. A. 21 36m 52, Dec. +41° 16' 53'), which blazed forth suddenly last November, exhibiting a continuous spectrum with numerous bright lines, now gives monochromatic light, the spectrum consisting of a single bright line, corresponding in position to the characteristic line of gaseous nebulæ. From this fact Lord Lindsay infers that this star, which has now fallen to 10.5 magnitude, has actually become a planetary nebula, affording an instance of a remarkable reversal of the process imagined by Laplace in his nebular theory.

Lord Lindsay's discovery is, according to Mr. Christie, of Greenwich, “confirmed by an examination of drawings of the spectrum of this star at five epochs between 1876, Dec. 8, and 1877, March 2, given by Dr. Vogel in a paper summarizing his own observations as well as those of other observers. Though in themselves these are not sufficient to indicate the conversion to a nebula, they acquire great importance in the light of the Dun-Echt observation, for they show clearly the progressive fading out, not only of the continuous spectrum, but also of the hydrogen and other bright lines."

This new star in Cygnus has been the subject of observation by Cornu, Copeland, and Vogel by means of the spectroscope; and from all the observations it is plain that the hydrogen lines at first prominent have gradually faded. With the decrease in their brilliancy, a line corresponding in position with the brightest of the lines of a nebula has strengthened. On December 8, 1876, this last line was much fainter than F, while on March 2, F was very much the fainter of the two. Lockyer, in commenting upon these facts, says that it has been shown by Croll that if the incandescence of this star came from the collision of two bodies, each having half the mass of our sun, and moving 476 miles per second, enough light and heat would be produced to cover the sun's radiation (at the present rate) for 50,000,000 years. As so much light, etc., has not been produced, Lockyer argues that this body“ might weigh only a few tons or even hundred-weights," and that it may therefore be quite near to us, and he suggests that accurate observations for position may indicate a motion.

Mr. S. C. Chandler, of New York, gives in the Astronomische Nachrichten, No. 2119, the results of his observations in 1875 on twenty-five variable stars. Anomalies have been detected in the light curve of R. Sagitto which point out the necessity of further examination. This series is noteworthy as being the only one made in the United States (we believe) since Masterman's, published in Gould's Astronomical Journal.

Dr. Schmidt, of Athens, communicates to the Astronomische Nachrichten a long series of variable star observations made in 1876.

A new work of 113 pages quarto on the photometry of the fixed stars, by Wolff, is published at Leipzig.

Klein, of Cologne, formerly announced that Alpha Urso Majoris periodically changed color from an intense fiery red to a yellow or yellowish-red every five weeks. Weber, of Peckeloh, has observed this star during August, September, October, and part of November, 1876, and finds this period to be about thirty-five days, as before. This periodic change of color must, then, be admitted, and it is the first one which rests on a sure basis, and which regularly recurs at short intervals.

Pogson's catalogue and maps of variable stars are referred to under the head of star catalogues.

Montigny, in the Bulletin of the Belgian Academy, 1876, No. 8, publishes an elaborate discussion on the scintillation of stars.

Dr. Schmidt, of Athens, publishes in Astronomische Nachrichten, 2109, an important paper on meteors, which comprises the results of a thirty-four years' series of observations.

P. Secchi has drawn up a list of 444 stars of marked color, giving their positions for 1870, as well as magnitudes and notes on the color. “This is a considerable enlargement of Schjellerup's Catalogue, which contains 280 red stars; but that it is very far indeed from being exhaustive is shown by the circumstance that M. Fearnley, at Christiania, has noted no fewer than thirty-four such objects in observing a zone of about 5°. In fact, it would seem that the comparative rarity of red stars in catalogues is simply due to the observer's attention not having been directed to this point; and there can be little doubt that a large number of stars of the sixth magnitude and under will be found on careful examination to be decidedly red.”

DOUBLE, MULTIPLE, AND BINARY STARS. A general catalogue of double stars is now printing which will probably be found to fulfil all the conditions for a work of this class. It is from the hands of Mr. Burnham, of Chicago, and is the work of many years.

It will contain all the elements of position (for 1880) with the particulars concerning each star from the latest trustworthy authority, and

copious notes referring to previous measures. For important stars the entire history is given or rendered accessible, a special treatment having been adopted for binaries. It is to be printed as an Appendix to the Washington Astronomical Observations for 1876, and will be eagerly looked forward to by all to whom such a work is a daily need.

The Observatory at Cincinnati has begun its work, since its removal to its new site, by researches in this field. The former observations of Mitchell have been reduced and published, and also a series of measures of double stars of southern declination. It is announced by the director, Professor Stone, that it is the plan of the Observatory to observe the doubles lying in the zone between 15° and 35° S. The great number of measures made by Otto v. Struve, at Pulkova, have been reduced and printed, but no copy has yet reached the United States. Recent measures of a large number of Struve's doubles are, however, available in the work of Dunér, of Lund. This includes 2679 observations made in the nine years from 1867 to 1875. Measures of many of the doubles, arranged in chronological order, accompanied by a tolerably full discussion of the whole series of observations, from Herschel's to Dunér's, are given. A table is added in which the stars are arranged in classes according to the arc through which they have moved since the earliest observation.

Class I. contains those stars which have moved through a complete revolution, and comprises 8 stars.

Class II., those stars which have moved through 180° of their apparent orbit—8 stars.

Class III., those which have moved through 90°—8 stars. Class IV., those which have moved through 30°—16 stars. Class V., those which have moved through 10°—48 stars.

Class VI., those which certainly have an orbital motion59 stars, etc., etc. So that there are 147 stars in this list which have been proved to be binary in character.

The recent measures of Dembowski, Ferrari, Schiaparelli, Wilson and Seabroke, Hall, Newcomb, Gledhill, and others are noteworthy, as well as the theoretical researches of Doberck on binaries, but they are too numerous to be referred to in detail.

The work of Lord Lindsay (“Publications of the Dun-Echt Observatory," vol. i.) is intended to supply the place of a gen

« EelmineJätka »