Prof. E. C. Pickering thinks that the fluctuations of light of the well-known variable star R Coronæ (in the Northern Crown), “are unlike those of any known variable.” This very curious object—one of the most curious in the heavens—sometimes remains for many months almost constant in brightness (just visible to the naked eye), and then rapidly fades in light by several magnitudes! Thus its changes of light in April and May, 1905, were as follows:—

1905,April1 ... ... 6·0magnitude
"11 ... ... 7·3"
"12 ... ... 8·4"
May1 ... ... 11·4"
"7 ... ... 12·5"

Thus between April 1 and May 1, its light was reduced by over 5 magnitudes. In other words, the light of the star on May 1 was reduced to less than one-hundredth of its light on April 1. If our sun were to behave in this way nearly all life would soon be destroyed on the face of the earth.

M. H. E. Lau finds that the short-period variable star δ Cephei varies slightly in colour as well as in light, and that the colour curve is parallel to the light curve. Near the minimum of light the colour is reddish yellow, almost as red as ζ Cephei; a day later it is pure yellow, and of about the same colour as the neighbouring ε Cephei.[332] But it would not be easy to fully establish such slight variations of tint.

A remarkably bright maximum of the famous variable Mira Ceti occurred in 1906. In December of that year it was fully 2nd magnitude. The present writer estimated it 1·8, or nearly equal to the brightest on record—1·7 observed by Sir William Herschel and Wargentin in the year 1779. From photographs of the spectrum taken by Mr. Slipher at the Lowell Observatory in 1907, he finds strong indications of the presence of the rather rare element vanadium in the star’s surroundings. Prof. Campbell finds with the Mills spectrograph attached to the great 36-inch telescope of the Lick Observatory that Mira is receding from the earth at the apparently constant velocity of about 38 miles a second.[333] This, of course, has nothing to do with the variation in the star’s light. Prof. Campbell failed to see any trace of the green line of hydrogen in the star’s spectrum, while two other lines of the hydrogen series “glowed with singular intensity.”

Mr. Newall has found evidence of the element titanium in the spectrum of Betelgeuse (α Orionis); Mr. Goatcher and Mr. Lunt (of the Cape Observatory) find tin in Antares (and Scorpii). If the latter observation is confirmed it will be the first time this metal has been found in a star’s atmosphere.[334]

It is a curious fact that Al-Sufi (tenth century) does not mention the star ε Aquilæ, which lies closely north-west of ζ Aquilæ, as it is now quite conspicuous to the naked eye. It was suspected of variation by Sir William Herschel. It was first recorded by Tycho Brahé about 1590, and he called it 3rd magnitude. Bayer also rated it 3, and since his time it has been variously estimated from 3½ to 4. If it was anything like its present brightness (4·21 Harvard) in the tenth century it seems difficult to explain how it could have escaped Al-Sufi’s careful scrutiny of the heavens, unless it is variable. Its colour seems reddish to me.

Mr. W. T. Lynn has shown—and I think conclusively—that the so-called “new star” of A.D. 389 (which is said to have appeared near Altair in the Eagle) was really a comet.[335]

Near the place of Tycho Brahé’s great new star of 1572 (the “Pilgrim Star”), Hind and W. E. Plummer observed a small star (No. 129 of d’Arrest’s catalogue of the region) which seemed to show small fluctuations of light, which “scarcely include a whole magnitude.” This may possibly be identical with Tycho Brahé’s wonderful star, and should be watched by observers. The place of this small star is (for 1865) R.A. 0h 17m 18s, N.P.D. 26° 37′·1. The region was examined by Prof. Burnham in 1890 with the 36-inch telescope of the Lick Observatory. “None of the faint stars near the place presented any peculiarity worthy of remark, but three double stars were found.”[336]

With reference to the famous Nova (T) Coronæ—the “Blaze Star” of 1866—Prof. Barnard finds from careful comparisons with small stars in its vicinity that “the Nova is now essentially of the same brightness it was before the outburst of 1866 ... there seems to be no indication of motion in the Nova.”