NOTICES FROM THE LICK OBSERVATORY.*

PREPARED BY MEMBERS OF THE STAFF.

DOUBLE-STAR NOTES.

The weather in the year 1899, taken as a whole, was not as favorable for double-star observations as during the year or two preceding. In the first three months, and again in the last three months, of the year, long spells of stormy or cloudy weather interfered seriously with the continuity of observations; and the month of August, usually a good observing month, had but very few nights when the seeing was good enough for the measurement of close pairs. Two hundred and fifty-five double stars were, however, measured during the year, 154 of them being under 1" in distance, and many of them near the limit of the separating power of even the large refractor.

This list includes nearly all the more rapid binary systems, many of the more difficult ẞ stars, and forty-seven new pairs, all under 5", which were found with the twelve-inch telescope. The detailed measures will be published in the Astronomische Nachrichten; but notes on some of the more important stars will be of interest.

Procyon: Measures of SCHAEBERLE'S companion on three nights give the following position:—

1899.99 334-5 4".88

SCHAEBERLE's discovery position was

1896.874 318°.8 4"-59

The companion is very faint-not brighter than 131⁄2 magnitude - and can only be seen well enough for good measures on the best nights. It is now much harder to measure than the companion to Sirius.

Sirius: The companion is increasing its distance from the bright star, and continues its motion in angle. The means of

* Lick Astronomical Department of the University of California.

five measures in angle and four in distance, including measures on one night in this year, are:

1899.896 145°.6 4"-53

ZWIERS's ephemeris gives for the same date, 147°.2 4′′.55. B 883: This close and interesting pair was measured on ten nights during the year. The mean of the measures on the last two nights is

1899.906 56°.5 0.24

Since I began observing this pair in the autumn of 1896, I have measured it on thirty-two different nights the longest intervals between two successive measures in the past two years being 04 years in the spring of 1898, and 0.3 years in the spring of 1899. As the angular change in three years, from 1896.88 to 1899.91, has been only 40°, I think it is now safe to say that this system cannot have a period at all approximating five and a half years. In fact, it seems very possible that the period may finally be found to be more nearly twenty years, as the consecutive character of the measures makes it practically certain that no change of quadrant has taken place in the last two years.

Andromeda: Measures of this pair on three excellent nights in July give:

1899.557 231°.0 0.23

The smaller star has been assumed to be in the first quadrant for the last few years; and the angular change since discovery in 1851 as more than 250°. But on these three nights the quadrant was noted with particular care, and as the difference of brightness of the components is nearly one magnitude, and the atmospheric conditions were most favorable, the position here given is undoubtedly correct. The period of revolution of this pair, too, is therefore much greater than has been supposed,

B 1007: This is one of the pairs found by BURNHAM with the twelve-inch refractor during his stay on Mt. Hamilton, in November, 1881. The mean of two nights' measures then gave:

1881.86 266°.2 0.27

Subsequently, BURNHAM was unable to see the star double with the 181⁄2-inch Dearborn refractor; and in the years 1890-92 he noted it as single with the thirty-six-inch refractor. During the past year the companion has again appeared in the same quadrant

as in 1881. A measure in 1899.177 gave 244°.3 o".18, and two later measures give as mean:—

The star is apparently in rapid motion, probably in an orbit whose plane is nearly parallel to the line of sight.

ẞ 524 = 20 Persei. This is one of the closest pairs measured during the year. The four measures secured are:

The angle given by the second measure is not in good accord with the other values, and may contain an error of circle reading. The pair, however, is so close and difficult under the best conditions that I have not felt at liberty to reject the discordant BURNHAM'S discovery position was

measure.

1878.66 338°.7 0.34

and his last measure with the thirty-six-inch refractor,

1891.79 281.7 0.15

If the above positions are correct as to quadrant, the pair has, therefore, nearly completed a revolution since discovery.

Some of the other close pairs measured during the year are:

Σ 1989=π2 Ursæ Min., 1899.53 347.6 0.16

Eighteen other pairs, with distances of less than one quarter of a second of arc, were measured during the year, the closest pair of all being perhaps B 953. of which measures were possible on only one night. These give

1899.714 223.2 0.10

In 1898 the star was found to be single.

January, 1900.

R. G. AITKEN.

COMETS OF 1899.

Five comets in all were discovered during 1899. Of these two only were new, the remaining three being apparitions of shortperiod comets.

Comet a (1899 I) was discovered on March 3, 1899, by Dr. SWIFT, at the Lowe Observatory, Echo Mountain, California. At the time of discovery the comet was moving north and towards the Sun, which it passed on April 12th. During some weeks it was lost while near the Sun, but was picked up again early in May. It attained a north Declination of 57° on May 29th. After perihelion passage, which occurred on April 13th, the comet became much brighter, being estimated at 3.0 magnitude on May 7th (HOLEtschek).

On May 11th, a second nucleus was observed, which was visible for two weeks.*

The last observation at Mt. Hamilton was on July 31st.

Comet b (1899 III), TUTTLE'S periodic comet, was rediscovered by Dr. MAX WOLF, at Heidelberg, by means of photography, on March 5th. It was then of 12th magnitude. Its brightness increased as it approached perihelion, which was passed on May 4th. It was last observed in the northern hemisphere on May 1st, when it became lost in the rays of the Sun. After perihelion passage it was observed in the southern hemisphere. This comet has a period of 13.8 years, and was observed at its last return in 1885.

Comet (1899 IV), TEMPEL'S second periodic comet, was rediscovered by the writer on May 6th. It was then of about the 16th magnitude, but increased rapidly in brightness as it neared both Sun and Earth. It passed perihelion on July 28th, at which time it was almost in opposition, and only thirty-five million miles distant from the Earth. At this time its brightness was of about the 8th magnitude. This opposition was one of the most favorable possible of this comet. It was last observed at the Lick Observatory on December 1st, when it was of only the 15th magnitude. This comet was observed on its last return to perihelion in 1894.

Comet d (1899 II), HOLMES's periodic comet, was rediscovered by the writer on June 10th. It was then very faintbeing estimated at 16th magnitude. This comet attracted much

*Publications A. S. P., No. 69, p. 150.

attention at the time of its discovery in 1892, when it was visible to the unaided eye. Its situation was practically as favorable for observation at this appearance as in 1892-93, and yet it has not been brighter than the 14th magnitude.

Perihelion was passed on April 28th. The last observation at Mt. Hamilton was on December 24th.

Comet e (1899 V) was discovered by M. GIACOBINI, at Nice, on September 29th. It was then of about the 11th magnitude. Perihelion was passed on September 15th, at a distance of one hundred and sixty-five million miles. Its brightness has decreased slowly. At the last observation, of December 23d, it was estimated to be of the 13th magnitude. It is now too near the Sun to be observed, but will in all probability be bright enough to be observed with large instruments in February or March. C. D. PERRINE.

1900, January 20.

NOTE ON THE SPECTRUM OF COMET a 1899 (SWIFT).

The spectra of the brightest comets of 1898 and 1899 were carefully observed at the Lick Observatory by Mr. WRIGHT.' His paper describing the results is published in the Astrophysical Journal for October, 1899. One fact established by the observations of SWIFT's Comet (1899 a) seems to me to be of great interest and importance.

Mr. WRIGHT's photograph of the spectrum records some fifteen bright lines, of which the lines at wave-lengths 4052, 3880, and 3870 are the strongest. "In the spectrum of the nucleus A 4052 is fully as bright as A 3870, but the latter line extends out into the comet's head more than four times as far as the former. In fact, the lines AA 3870 and 3880 experience only a gradual increase in brightness in the region of the nucleus, and extend the entire length of the slit. In the cases of all the other lines, the change is quite abrupt. This must be taken to indicate a marked difference between the spectrum of the nucleus and the spectra of the outer parts of the head."

The lines at AA 3870 and 3880 are due to cyanogen.

It seems not too much to hope that this beginning in detecting differences in the spectra of different parts of comets may, in the case of very bright comets, be extended over larger areas and in greater detail; leading, as in the case of the Sun, to a better understanding of their condition and constitution. W. W. C.