Having looked at α (Betelgeuse), the great topaz star on Orion's right shoulder, and admired the splendor of its color, we may turn the four-inch upon the star Σ 795, frequently referred to by its number as "52 Orionis." It consists of one star of the sixth and another of sixth and a half magnitude, only 1.5" apart, p. 200°. Having separated them with a power of two hundred and fifty diameters on the four-inch, we may try them with a high power on the three-inch. We shall only succeed this time if our glass is of first-rate quality and the air is perfectly steady.
The star λ in Orion's head presents an easy conquest for the three-inch, as it consists of a light-yellow star of magnitude three and a half and a reddish companion of the sixth magnitude; distance 4", p. 43°. There is also a twelfth-magnitude star at 27", p. 183°, and a tenth or eleventh magnitude one at 149", p. 278°. These are tests for the five-inch, and we must not be disappointed if we do not succeed in seeing the smaller one even with that aperture.
Other objects in Orion, to be found with the aid of our [map], are: Σ 627, a double star, magnitude six and a half and seven, distance 21", p. 260°; Ο Σ 98, otherwise named ι Orionis, double, magnitude six and seven, distance 1", p. 180°, requires five-inch glass; Σ 652, double, magnitudes six and a half and eight, distance 1.7", p. 184°; ρ, double, magnitudes five and eight and a half, the latter blue, distance 7", p. 62°, may be tried with a three-inch; τ, triple star, magnitudes four, ten and a half, and eleven, distances 36", p. 249°, and 36", p. 60°. Burnham discovered that the ten-and-a-half magnitude star is again double, distance 4", p. 50°. There is not much satisfaction in attempting τ Orionis with telescopes of ordinary apertures; Σ 629 otherwise m Orionis, double, magnitudes five and a half (greenish) and seven, distance 31.7", p. 28°, a pretty object; Σ 728, otherwise A 32, double, magnitudes five and seven, distance, 0.5" or less, p. 206°, a rapid binary,[2] which is at present too close for ordinary telescopes, although it was once within their reach; Σ 729, double, magnitudes six and eight, distance 2", p. 26°, the smaller star pale blue—try it with a four-inch, but five-inch is better; Σ 816, double, magnitudes six and half and eight and a half, distance 4", p. 289°; ψ 2, double, magnitudes five and a half and eleven, distance 3", or a little less, p. 322°; 905, star cluster, contains about twenty stars from the eighth to the eleventh magnitude; 1267, nebula, faint, containing a triple star of the eighth magnitude, two of whose components are 51" apart, while the third is only 1.7" from its companion, p. 85°; 1376, star cluster, small and crowded; 1361, star cluster, triangular shape, containing thirty stars, seventh to tenth magnitudes, one of which is a double, distance 2.4".
Let us now leave the inviting star-fields of Orion and take a glance at the little constellation of Lepus, crouching at the feet of the mythical giant. We may begin with a new kind of object, the celebrated red variable R Leporis ([map No. 1]). This star varies from the sixth or seventh magnitude to magnitude eight and a half in a period of four hundred and twenty-four days. Hind's picturesque description of its color has frequently been quoted. He said it is "of the most intense crimson, resembling a blood-drop on the black ground of the sky." It is important to remember that this star is reddest when faintest, so that if we chance to see it near its maximum of brightness it will not impress us as being crimson at all, but rather a dull, coppery red. Its spectrum indicates that it is smothered with absorbing vapors, a sun near extinction which, at intervals, experiences an accession of energy and bursts through its stifling envelope with explosive radiance, only to faint and sink once more. It is well to use our largest aperture in examining this star.
We may also employ the five-inch for an inspection of the double star ι, whose chief component of the fifth magnitude is beautifully tinged with green. The smaller companion is very faint, eleventh magnitude, and the distance is about 13", p. 337°.
Another fine double in Lepus is κ, to be found just below ι; the components are of the fifth and eighth magnitudes, pale yellow and blue respectively, distance 2.5", p. 360°; the third-magnitude star α has a tenth-magnitude companion at a distance of 35", p. 156°, and its neighbor β ([map No. 2]), according to Burnham, is attended by three eleventh-magnitude stars, two of which are at distances of 206", p. 75°, and 240", p. 58°, respectively, while the third is less than 3" from β, p. 288°; the star γ ([map No. 2]) is a wide double, the distance being 94", and the magnitudes four and eight. The star numbered 45 is a remarkable multiple, but the components are too faint to possess much interest for those who are not armed with very powerful telescopes.
From Lepus we pass to Canis Major ([map No. 2]). There is no hope of our being able to see the companion of α (Sirius), at present (1901), even with our five-inch. Discovered by Alvan Clark with an eighteen-inch telescope in 1862, when its distance was 10" from the center of Sirius, this ninth-magnitude star has since been swallowed up in the blaze of its great primary. At first, it slightly increased its distance, and from 1868 until 1879 most of the measures made by different observers considerably exceeded 11". Then it began to close up, and in 1890 the distance scarcely exceeded 4". Burnham was the last to catch sight of it with the Lick telescope in that year. After that no human eye saw it until 1896, when it was rediscovered at the Lick Observatory. Since then the distance has gradually increased to nearly 5". According to Burnham, its periodic time is about fifty-three years, and its nearest approach to Sirius should have taken place in the middle of 1892. Later calculations reduce the periodic time to forty-eight or forty-nine years. If we can not see the companion of the Dog Star with our instruments, we can at least, while admiring the splendor of that dazzling orb, reflect with profit upon the fact that although the companion is ten thousand times less bright than Sirius, it is half as massive as its brilliant neighbor. Imagine a subluminous body half as ponderous as the sun to be set revolving round it somewhere between Uranus and Neptune. Remember that that body would possess one hundred and sixty-five thousand times the gravitating energy of the earth, and that five hundred and twenty Jupiters would be required to equal its power of attraction, and then consider the consequences to our easy-going planets! Plainly the solar system is not cut according to the Sirian fashion. We shall hardly find a more remarkable coupling of celestial bodies until we come, on another evening, to a star that began, ages ago, to amaze the thoughtful and inspire the superstitious with dread—the wonderful Algol in Perseus.
We may remark in passing that Sirius is the brightest representative of the great spectroscopic type I, which includes more than half of all the stars yet studied, and which is characterized by a white or bluish-white color, and a spectrum possessing few or at best faint metallic lines, but remarkably broad, black, and intense lines of hydrogen. The inference is that Sirius is surrounded by an enormous atmosphere of hydrogen, and that the intensity of its radiation is greater, surface for surface, than that of the sun. There is historical evidence to support the assertion, improbable in itself, that Sirius, within eighteen hundred years, has changed color from red to white.