레오-라이온

Leo - The Lion

Leo is one of the most familiar constellations in the sky. It has been recognized as a lion since ancient times. Look for a pattern of stars resembling a backwards question mark; this represents the head of the lion. The bright star Regulus is at the bottom of the figure. For northern observers, Leo is best viewed from February through July.

The Leonid meteor shower occurs around November 17th of each year. Normally, the Leonids only produce about 12 meteors per hour, but in certain years (most recently 1933 and 1966) this shower has become a "meteor storm" producing thousands of meteors per hour. This is believed to be due to the Earth's passage through a debris cloud from the comet which produced the material that generates the Leonid meteors.

History and Mythology

Leo is the Latin word for lion. The constellation Leo was recorded by Ptolemy in the second century AD and is the fourth constellation of the zodiac. It is, however, far older than the time of Ptolemy and was known to the ancient Babylonians as UR.GU.LA. Like most of the zodiac constellations, Leo is believed to have been recorded as far back as 1000 BCE in the MUL.APIN tablets or even earlier.



Leo, from Johann Bayer's 1603 star atlas, Uranometria.The shaded area is the Zodiacal region around the Ecliptic.
The Greeks believed that Leo represented the Nemean lion that stalked and devoured the inhabitants of the town that serves as its namesake. Hercules' first of twelve labors was to kill the beast. Like many of the monstrous beasts that confronted heroes in Greek mythology, the Nemean lion was said to be the offspring of Typhon and Echidna. It was born with skin supposedly impervious to all weaponry. Hercules was unable to pierce its skin despite his mighty strength and so resorted to choking the beast to death. After completing the task, Hercules used the lion's own claws to skin it, donning the pelt as armor.

To the Chinese, many of the stars in Leo, including the sickle from heart to head, are part of the large constellation Xuanyuan, the Yellow Dragon. The constellation is also highly prevalent in Egyptian astrology. The sun rose in Leo during the summer months heralding the rise of the Nile River. To the Egyptians the Nile flood brought with it new soil and the beginnings of new life. Leo also held many of these associations was possibly considered the sign under which the sun was born. Leo's position during the summer in the Northern Hemisphere heralded lions near the Nile trying to survive the summer heat.

Notable Stars

Alpha Leonis, or Regulus, is a first magnitude star; its name is Latin for "Prince". It marks the handle of a group of stars forming the "sickle" or reversed question mark which marks the lion's head. Regulus is the 21st brightest star in the sky. It is a blue-white star with 240 times the luminosity of the Sun, shining from 78 light-years away. It spins extremely rapidly, with a rotation period of 16 hours; this causes it to have a highly oblate shape.

Denebola, or Beta Leonis, is the second brightest star in Leo and is located at eastern end of the lion's tail. Its name is shortened from the Arabic phrase meaning "tail of the Lion." It is a white second-magnitude star physically similar to Sirius, but 34 light-years away, as opposed to Sirius' 8.7.

At the lion's shoulder is the impressive third magnitude double star Gamma Leonis, or Algieba. Algieba's name means "forehead" in Arabic. It consists of an orange second magnitude primary with a third magnitude yellow companion, separated by 4 arcseconds. The system is 125 light-years away and has an orbital period over 500 years.

Delta Leonis, or Zosma, has a Greek name which means "girdle". At magnitude 2.6, it is Leo's 4th-brightest star; it is 58 light-years away.

Leo also contains the 13th magnitude red dwarf star Wolf 359. Much too dim to see except with large telescopes, this star is only 7.8 light-years away, and is the third-closest star system to Earth. In the Star Trek universe, the Battle of Wolf 359 takes place with the Borg Collective in the year 2367.

Clusters, Nebulae, and Galaxies

The galaxies M 95 and M 96 form a pair near the middle of Leo. M 95 is a barred spiral, and M 96 has a dust lane which extends through the nucleus. Near them is M 105, a giant elliptical galaxy of magnitude 9.3. All three are members of the Leo I group of galaxies about 35 to 40 million light-years away.

The galaxies M 95 (left), M 96 (middle), and M 105 (brightest at bottom right) in Leo, by Rob Gendler.
The most impressive objects in Leo are M 65 and M 66. They are both spiral galaxies on the eastern end of the constellation. M 65 is a highly inclined spiral with a prominent dust lane extending across the disk of the galaxy.

Galaxy M 65. Doc. G. and Dick Goddard/Adam Block/NOAO/AURA/NSF.
M 66 is a spiral with two bright arms which loop outward from the nucleus. This galaxies are best seen with an 8-inch or larger telescope. Along with the nearby tenth magnitude spiral galaxy NGC 3628, M 65 and M66 make up the famous "Leo Triplet."

The neighbor of M 65 in Leo, M 66. Jim Misti.
Other noteworthy galaxies in Leo include NGC 2903, a ninth magnitude spiral viewed at an oblique angle from 20 million light-years away; the elliptical galaxy NGC 3384, about 35 million light-years away; and the ninth magnitude spiral galaxy NGC 3521, also 35 million light-years away.