discovered in the Southern Constellation (Antlia) has the surprisingly short period of only seven and three quarters hours—the most rapid variation hitherto detected in any variable star. All the Algol variables are white, or only slightly colored.
It was long since suggested that the periodical diminution of light in the Algol variables might possibly be due to the interposition of a dark, eclipsing satellite. Some few years since Prof. Pickering undertook a mathematical investigation of the case of Algol, and showed that an eclipsing satellite revolving in a nearly circular orbit in a period indicated by the light-variations of the star would satisfactorily explain the observed phenomenon within the limits, of errors of observation, and he suggested that the orbit might be determined by spectroscopic observation of the star's light before and after the minimum. Observations of this kind made by Prof. Vogel at Potsdam, in 1888 and 1889, leave little doubt that the decrease of light is really due to an eclipsing satellite. He found that before the minimum the bright star is receding from the earth (and therefore the dark companion approaching), and after minimum it is approaching, thus proving the eclipse theory to be correct.
Herr J. Plassmann, of Warendorf, Germany, has lately announced his discovery of a secondary minimum in the light of Algol and Lambda Tauri. This, if confirmed, would seem to show that the eclipsing satellite is not absolutely dark, but possesses some inherent light of its own, this light being cut off when the satellite passes in its turn behind the disk of its primary.—The Gentleman's Magazine.
