Sirius

Sirius, otherwise called Canicula, or the Dog-star, the brightest star in the heavens, is situated in the constellation of Canis Major, or the 'Great Dog.' Its distance in light-units is 8.6 (see STARS). It has long been known to possess a 'proper motion'—i.e. an independent progressive motion—which was for a time believed to be in a straight line, but was in 1844 shown by Bessel to consist of an undulatory progressive motion on each side of a middle line. This motion was investigated by Professor Peters of the Pulkowa Observatory, Russia, on the supposition that its anomalous character was produced by the attraction of some unseen neighbour, and his calculations were completed and verified by Mr Safford of Washington. In January 1862 Mr Alvan Clark of New York, chancing to observe Sirius through a powerful telescope, detected a minute star (which had never before been observed) situated at an angular distance of 7" from Sirius, and it is generally believed that this is the disturber in question. By photometric measurement it has been shown that, adopting the latest measures of its distance, Sirius gives seventy times as much light as our sun would at the same distance, and has a mass three times that of the sun. The Egyptians called this star Sothis, and at one time its 'Heliacal Rising' (q.v.) was regarded as a sure forerunner of the rising of the Nile; while among the Romans it was considered a star of evil omen, whose appearance above the horizon coincided with (or even caused) the unhealthy and oppressive heats of summer. Hence the origin of the various superstitions regarding the Dog-days (q.v.), many of which are still current. The term 'dog-star' was also applied to Procyon, a bright star in Canis Minor, whose heliacal rising differs only by a few days from that of Sirius.