The stars α1 and α2 Libræ form a wide double, perhaps just separable by the naked eye in very favourable weather. The larger component is of the third, the smaller of the sixth magnitude, the former yellow the latter light grey.
The star β Libræ is a beautiful light-green star to the naked eye; in the telescope a wide double, pale emerald and light blue.
In Scorpio there are several very beautiful objects:—
The star Antares or Cor Scorpionis is one of the most beautiful of the red stars. It has been termed the Sirius of red stars, a term better merited perhaps by Aldebaran, save for this that, in our latitude, Antares is, like Sirius, always seen as a brilliant "scintillator" (because always low down), whereas Aldebaran rises high above the horizon. Antares is a double star, its companion being a minute green star. In southern latitudes the companion of Antares may be seen with a good 4-inch, but in our latitudes a larger opening is wanted. Mr. Dawes once saw the companion of Antares shining alone for seven seconds, the primary being hidden by the moon. He found that the colour of the secondary is not merely the effect of contrast, but that this small star is really a green sun.
The star β Scorpionis is a fine double, the components 13"·1 apart, their magnitudes 2 and 5½, colours white and lilac. It has been supposed that this pair is only an optical double, but a long time must elapse before a decisive opinion can be pronounced on such a point.
The star σ Scorpionis is a wider but much more difficult double, the smaller component being below the 9th magnitude. The colour of the primary (4) is white, that of the secondary maroon.
The star ξ Scorpionis is a neat double, the components 7"·2 apart, their magnitudes 4½ and 7½, their colours white and grey. This star is really triple, a fifth-magnitude star lying close to the primary.
In Ophiuchus, a constellation covering a wide space immediately above Scorpio, there are several fine doubles. Among others—
39 Ophiuchi, distance between components 12"·1, their magnitudes 5½ and 7½, their colours orange and blue.
The star 70 Ophiuchi, a fourth-magnitude star on the right shoulder of Ophiuchus, is a noted double. The distance between the components about 5½", their magnitudes 4½ and 7, the colours yellow and red. The pair form a system whose period of revolution is about 95 years.