Leo, the Lion, is a zodiacal constellation that heralds the start of spring and galaxy season. It lies on the ecliptic between the constellations of Cancer and Virgo. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Leo is another ancient constellation that may date as far back as the Mesopotamian civilization 4,000 years ago. Greek mythology identified Leo with the Nemean Lion who was killed by Hercules in the first of his twelve labors. The Lion was placed among the stars because it was the king of the beasts. The head of the Lion is distinguished by an asterism that looks like a sickle or backwards question mark anchored by Regulus. Regulus is Alpha Leonis, a spectral-class B-type blue star that shines at an apparent magnitude of 1.36. It is located 79 light-years away from the Earth. Regulus means the "Little King" in Latin. Regulus is a quadruple star system. The primary star, Regulus A, is believed to be a close spectroscopic binary with a white dwarf as a companion. The secondary star, itself also a binary, can be seen at a distance of 175 arcseconds from Regulus A. That secondary star is comprised of Regulus B (magnitude 8.1) and Regulus C (magnitude 13.5). These two stars are separated by 4 arcseconds. Beta Leonis is Denebola, a spectral-type A blue-white star that shines at magnitude 2.13 and is 36 light-years away. Denebola means the "Tail of the Lion" in Arabic. Denebola anchors the triangle asterism at the tail of the Lion that points to the Virgo Cluster of galaxies. Gamma Leonis is Algieba, a very beautiful blue and gold double star with magnitudes of 2.3 and 3.6, and an apparent separation of 4 arcseconds that is located 130 light-years from Earth. Algieba means the "Forehead" in Arabic. Wolf 359 (CN Leonis), a star familiar to science fiction and Star Trek fans, is a magnitude 13.5 red dwarf that is one of the nearest stars to Earth, at a distance of only 7.78 light-years. Leo lies far away from the Milky Way, so it doesn't contain any bright nebulae, but it does have a number of interesting galaxies, such as the Leo Trio (M65, M66, NGC 3628), Leo 1, a dwarf spheroidal galaxy close to Regulus, M95, M96, M105, and the Hickson 44 compact galaxy group. The Sun is located in the constellation of Leo from August 10 to September 16. Leo was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 12th largest of today's 88 modern constellations, covering 947 square degrees of sky. North is to the lower left in the above image.
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