Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is (), a corruption of the initial letter of Λεων (Leon). Leo lies between dim Cancer to the west and Virgo to the east.

Notable features

Stars

Leo contains many bright stars, such as Regulus (α Leonis), the lion's tail; Denebola (β Leonis); and γ¹ Leonis (Algieba). Many other fainter stars have been named as well, such as δ Leo (Zosma), θ Leo (Chort), κ Leo (Al Minliar al Asad ), λ Leo (Alterf), and ο Leo (Subra).

Regulus, η Leonis, and γ Leonis, together with the fainter stars ζ Leo (Adhafera), μ Leo (Ras Elased Borealis), and ε Leo (Ras Elased Australis), make up the asterism known as the Sickle. These stars represent the head and the mane of the lion.

The star Wolf 359, one of the nearest stars to Earth (7.7 light-years), is in Leo. Gliese 436, a faint star in Leo about 33 light years away from the Sun, is orbited by one of the smallest extrasolar planets ever found.

The carbon star CW Leo (IRC +10216) is the brightest star in the night sky at the infrared N-band (10 μm wavelength).

Deep sky objects

Leo contains many bright galaxies, of which Messier 65, Messier 66, Messier 95, and Messier 96 are the most famous, the first two being part of the Leo Triplet.

The Leo Ring, a cloud of hydrogen and helium gas left over from the Big Bang, is found in orbit of two galaxies found within this constellation.

History and mythology

Leo has been represented as a lion by numerous civilizations for thousands of years. One explanation is that the Sun was among its stars in Midsummer, and during this time the lions of the Egyptian desert left their accustomed haunts for the banks of the Nile, where they could find relief from the heat in the waters of the inundation. Pliny wrote that the Egyptians worshipped the stars of Leo because the rise of their great river was coincident with the Sun's entrance among them. Distinct reference is made to Leo in an inscription of the walls of the Ramesseum at Thebes, which, like the Nile temples generally, was adorned with the animal's bristles, while on the planisphere of Dendera its figure is shown standing on an outstretched serpent. The Egyptian stellar Lion, however, comprised only a part of the modern constellation, and in the earliest records some of its stars were shown as a knife, whereas they now are as a sickle. Kircher gave its title there as Πιμεντεκεων, Cubitus NiliRichard Hinckley Allen's Star Names: Their Lore and Meaning, at LacusCurtius.

The Persians called Leo Ser or Shir; the Turks, Artan; the Syrians, Aryo; the Jewish, Arye; the Indians, Simha ; and the Babylonians, Aru — all meaning a lion. In Euphratean astronomy it was additionally known as Gisbar-namru-sa-pan, variously translated, but by Bertin, as the Shining Disc which precedes Bel, "Bel" being our Ursa Major, or in some way intimately connected therewith.

In Greek mythology, it was identified as the Nemean Lion which was killed by Hercules during one of his twelve labours, and subsequently put into the sky.

The Roman poet Ovid called it Herculeus Leo and Violentus Leo. Bacchi Sidus (Star of Bacchus) was another of its titles, the god Bacchus always being identified with this animal. However, Manilius called it Jovis et Junonis Sidus (Star of Jupiter and Juno).

Early Hindu astronomers knew it as Asleha and as Sinha, the Tamil Simham but later, influenced by Greece and Rome, as Leya or Loin, from the word Leo, as the Romans commonly called it.

Astrology

, the Sun appears in the constellation Leo from August 10 to September 15. In tropical astrology, the Sun is considered to be in the sign Leo from July 24 to August 23, and in sidereal astrology, from August 16 to September 15.

Visualizations

Leo, with Leo Minor above, as depicted in , a set of constellation cards published in London c.1825.

Leo is commonly represented as if the sickle-shaped asterism of stars is the back of the Lion's head.

Diagram of H.A. Rey's alternative way to connect the stars of the constellation Leo. The lion is shown walking.

H.A. Rey has suggested an alternative way to connect the stars, which graphically shows a lion walking. The stars delta Leonis, gamma Leonis, eta Leonis, and theta Leonis form the body of the lion, with gamma Leonis being of the second magnitude and delta Leonis and theta Leonis being of the third magnitude. The stars gamma Leonis, zeta Leonis, mu Leonis, epsilon Leonis, and eta Leonis form the lion's neck, with epsilon Leonis being of the third magnitude. The stars mu Leonis, kappa Leonis, lambda Leonis, and epsilon Leonis form the head of the lion. Delta Leonis and beta Leonis form the lion's tail: beta Leonis, also known as Denebola, is the bright tip of the tail with a magnitude of two. The stars theta Leonis, iota Leonis, and sigma Leonis form the left hind leg of the lion, with sigma Leonis being the foot. The stars theta Leonis and rho Leonis form the right hind leg, with rho Leonis being the foot. The stars eta Leonis and alpha Leonis mark the lion's heart, with alpha Leonis, also known as Regulus, being the bright star of magnitude one. The stars eta Leonis and omicron Leonis form the right front foot of the Lion.

Citations