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LEO
The Lion
Leo - Alexander Jamieson - 1822
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The figure of a lion was put into the heavens to commemorate the first of the great labours of Hercules: the killing of the monstrous, man-eating lion of Nemaea. According to legend, Hercules broke all his weapons trying to kill the lion, and finally had to resort to strangling the beast with his bare hands. Such a feat certainly earned recognition, and it is said that Hercules proudly wore the skin of the lion for the rest of his days. Leo is easily identified by the familiar asterism known as the Sickle of Leo, that looks like a backwards question mark, and depicts the head and mane of the lion. The prone body of the lion extends back, sphinx-like, with a bright triangle of stars depicting the rear of the lion.
Just as the lion is known as king of the beasts, the constellation Leo has been associated with kings and royalty throughout antiquity.
With a magnitude of 1.25, the brightest star in the constellation, Alpha Leonis, was named Regulus (Latin for little king), by the great Polish astronomer Copernicus. The star is also known as Cor Leonis - the heart of the lion. The ancients regarded it as one of the four "Royal Stars" of Heaven (the other three being Aldebaran, Fomalhaut, and Antares). Regulus is 85 light years away, and five times the diameter of our Sun.
With a magnitude of 2.14, the second brightest star in the constellation, Beta Leonis, is named Denebola, the tail of the lion. It is an A3 main sequence star, 43 light years away.
Al Geiba means the lion's mane. With a magnitude of 2.61, it is the brightest star in the curve of the sickle, and upon close examination can be seen as a binary, or double star system. It is 125 light years away, and the radiant from which the famous Leonid Meteors appear to originate. In January, 2011, a huge planet eight times the size of Jupiter was discovered in orbit around this star. It is highly probable that there are more, smaller planets orbiting this star as well. They will be harder to detect, of course, but there are a lot of people looking for them, so stay tuned.
The constellation Leo is, in fact, full of exoplanets. No less than 19 have been discovered so far. But Al Geiba is the only parent star bright enough to see with the naked eye. For the most recent exoplanet discoveries, see NASA's Planet Quest.
Zozma means the girdle. It is 80 light years away, and shines at a magnitude of 2.56.
Eta Leonis is a white supergiant star, with a radius 44 times that of our Sun. It is 16,000 times brighter than our Sun, yet only appears in our sky with a magnitude of 3.52. The reason it doesn't outshine everything else in the sky is because it is over 2,000 light years away. If it was as close as Sirius (the brightest star in the sky, only 9 light years away), Eta Leonis would be 50 times brighter than the brilliant planet Venus, and would be visible during the day.
Coxa (also known as Chort) means hip. It is 90 light years away, with a magnitude of 3.34.
The M66 Group, also known as the Leo Triplet, is 35 million light years away. It is a favorite target for small telescopes as it contains three galaxies all visible in the same field of view: M65 (upper right - magnitude 9.3), M66 (lower right - magnitude 8.9), NGC 3628 (lower left - magnitude 9.5).
Up by the head of the lion is the bright spiral galaxy NGC 2903. With a magnitude of 9.0, it is one of the brightest galaxies in the sky, and relatively easy to find in a small telescope. It is also oriented almost face-on, exposing a great deal of detail in its spiral arms. It is close, as galaxies go, only 20 million light years away.
The M96 Group of galaxies contains the relatively bright M95, M96, and M105 Messier objects, as well as a large number of smaller, dimmer galaxies, about 38 million light years away.
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