1911 Encyclopædia Britannica/Leo (constellation)
LEO (The Lion), in astronomy, the fifth sign of the zodiac (q.v.), denoted by the symbol Ω. It is also a constellation, mentioned by Eudoxus (4th century B.C.) and Aratus (3rd century B.C.). According to Greek mythology this constellation is the Nemean lion, which, after being killed by Hercules, was raised to the heavens by Jupiter in honour of Hercules. A part of Ptolemy’s Leo is now known as Coma Berenices (q.v.). α Leonis, also known as Cor Leonis or the Lion’s Heart, Regulus, Basilicus, &c., is a very bright star of magnitude 1.23, and parallax 0.02″, and proper motion 0.27″ per annum. γ Leonis is a very fine orange-yellow binary star, of magnitudes 2 and 4, and period 400 years. ι Leonis is a binary, composed of a 4th magnitude pale yellow star, and a 7th magnitude blue star. The Leonids are a meteoric swarm, appearing in November and radiating from this constellation (see Meteor).