Leo is one of the easiest constellations to recognize, and has been pictured as a lion by many different cultures since ancient times, including by the Indians, Persians, and Greeks. It is the 12th largest constellation in the night sky, and rather hard to miss with a ‘sickle of stars’ forming the front part of its distinctive sphinx-like figure. Leo contains the 22nd brightest star in the entire night sky, Regulus, a blue-white star located 77 light year from Earth, which also forms part of a distinctive asterism of stars called the Spring Triangle, together with Arcturus in Boötes, and Spica in Virgo.
Represents: the Nemean Lion
The First Labour of Heracles was to kill a fearsome lion that had been preying on people around the hills of Nemea in ancient Greece. Heracles could not kill the lion with arrows as its skin was impenetrable, so he trapped the man-eating lion in its cave and during a fierce struggle squeezed it to death, instead. Hercules then used one of its claws to skin the animal and thereafter wore its pelt as an impenetrable mantle to make him even more fearsome.
Shape: Sphinx/Lion Shape
Leo occupies an area of 947 square degrees, making it the third largest of the 12 zodiacal constellations, after Virgo and Aquarius. It is easily recognized as the majestic lion it depicts, while the grouping of six stars forming a backwards question-mark called the “Sickle” produces one of the night sky’s most striking asterisms, apart from the Big Dipper.
Location: A Northern Constellation
Leo is a northern sky constellation visible to observers between latitudes +90 and -65 degrees, and is simple to locate if you follow the Big Dipper’s’pointer stars‘ in the opposite direction from Polaris to an area where Leo can be found between Gemini and Cancer to the west, and Virgo to the east. Other nearby constellations include Hydra and Leo Minor, directly above Leo, as well as Coma Berenices, that is formed from the stars of thelion’s “tail”.
Best Seen: Spring
Leo is a winter constellation that is visible in the northern hemisphere from January to June, but rises to prominence around the time of the spring equinox in March. In the southern hemisphere, Leo can be seen during summer and autumn.
Notable Stars: Regulus (1st magnitude)
The constellation of Leo contains four stars of first or second magnitude, making it appear particularly prominent in the night sky. These stars include Regulus, Deneb, and Algieba:
– Regulus (Alpha Leonis) is a multiple system located about 77 light years away with an apparent visual magnitude of 1.35, making it the most luminous star in Leo, and the 22nd brightest star in the entire night sky. In actual fact, Regulus consists of two binary systems orbiting each other, with the primary system, Regulus A, a blue-white main-sequence star (B7V) orbiting a suspected white dwarf 0.35 AU away once every 40 days or so.
The other system consists of Regulus B, an orange dwarf (K1-2 V), and Regulus C, a red dwarf (M5 V) situated 4,200 AU away from the the main pair, separated by 100 AU, and with an orbital period of 2,000 years. Regulus, means “little king” in Latin, and is one of the stars from which longitude is reckoned, as it lies almost exactly on the ecliptic and is visible for eight months of the year.
– Algieba (Gamma Leonis), the constellation’s second brightest star, is a binary system situated 130 light years from our solar system of magnitude 2.28. Its primary star is an orange giant (K1-IIIbCN-0.5) that is 23 times bigger than the Sun, and at least 180 times brighter, while its dimmer companion, a yellow giant (G7IIICN-I) is 10 times bigger than the Sun and about 50 times as bright. The pair orbit each other once every 500 or so years, with a planet having been discovered orbiting the primary component. Algieba derives from the Arabic for ‘the forehead’, although the star actually marks the lion’s mane.
– Denebola (Beta Leonis), the third most luminous star in Leo, is a blue main sequence dwarf (A3 Va) found 36 light distant that shines with a visual magnitude of 2.14. It is around 200 million years old, and is 1.75 times the size of the Sun, and around 12 times brighter. The name Denebola comes from the Arabic phrase meaning ‘Tail of the Lion’.
Other stars of interest in Leo includes Zosma (“Hip of the Lion”), Ras Elased Australis (“Head of the Lion”), Chertan (“The Rib”), Subra (“Head of the Lion”), and Al Minliar al Asad (“Muzzle of the Lion”). The constellation also includes Wolf 359, a red dwarf star that at only 7.78 light years distant is one of the closest stars to Earth. It is about as small as an actual burning star can get, too, being just 8% of the mass of our Sun, and about the same size as Jupiter.
Notable Objects: Many Bright Galaxies
The constellation of Leo contains an impressive number of deep-sky objects (DSOs), including 5 Messier objects, namely the spiral galaxies M65, M66, M95, M96, and the elliptical galaxy M105. Nevertheless, there are plenty of other galaxies in Leo, such as NGC 3628, NGC 3607, NGC 3593, NGC 3384, NGC 3842, NGC 3596, NGC 2903, NGC 3626, and NGC 3357.
– Messier 65 (M65, NGC 3623) is an intermediate spiral galaxy, and at a distance of about 35 million light years, has an apparent visual magnitude of 10.25. This galaxy contains very little gas and dust, meaning that star formation no longer takes place in significant numbers, and thus the vast majority of its stars are very old.
– Messier 66 (M66, NGC 3627) is another intermediate spiral galaxy that is 36 million light years distant, and spread across 95 thousand light-years of space. It has an apparent visual magnitude of 8.9, and has had four recorded supernovae.
– Messier 95 (M95, NGC 3351) is a barred spiral galaxy that is about 38 million light years distant, and with an apparent visual magnitude of 11.4. M95 is also a member of the M96 Group of galaxies that includes M96 itself, M105, and at least nine other galaxies of various types. M95 is notable for the 2,000 light-year-diameter ring-shaped star-burst region around its core, as well as the fact that a supernova was detected in the galaxy in March of 2012.
Contains 2nd Biggest Structure in Universe
Leo also contains the second most massive astronomical structure yet discovered in the universe called the Huge-LQG (large quasar group). This enormous expanse consists of 73 quasars spread across 4 billion light-years of space. In comparison, our entire Milky Way is just 100,000 light-years across. The Huge-LQG is second in size only to the Hercules-Corona Borealis Great Wall, which is 10 billion light-years wide..
Meteor Showers: The Leonids (+3 others)
The constellation Leo is home to a number of meteor showers, including the following, with their peak dates; Delta Leonid (end of Feb), Sigma Leonid (April 17), Leonids (Nov 17th), and Leo Minorids (Dec 14).
Leo’s most prolific meteor shower, The Leonids, is associated with the comet Tempel-Tuttle, and is also one of the most spectacular meteor displays of the year. It is visible from November 13th to 21st, and peaks on November 17th when 20 or more meteors can be seen per hour. Once very 33 years, however, a periodic meteor storm takes place in which thousands can be seen every hour, with the next expected to occur in 2032. The biggest one is supposed to have occurred in 1833, with estimates placing the count at between 100,000 and 240,000 per hour – that’s right, up to 4,000 meteors per minute, 67 per second – for the 9 hours it rained down. In a famous piece of art work depicting the 1833 shower, you can see that, in a time when there were no indoor and outdoor lights, the scene is lit almost as brightly as daytime.
Planets: 18+ Known Planets
Leo has 15 stars with 18 known planets between them, although none of the stars in Leo have planets in their habitable zones.
Astrology: July 23 to Aug 22
Date of Birth: July 23 to August 22
Sign Ruler: Sun
Birth Stone: Peridot, Ruby
Color: Red, Gold, Yellow
Characteristics: Proud, Charitable, Reflective, Loyal, Enthusiastic
Compatibility: Aries, Sagittarius
Star Lore: Leo and the Nile River
Although it is not entirely clear how the constellation Leo became known to the ancient Egyptians, one enchanting piece of star lore goes as follows. The ancient Egyptians worshiped Leo because they knew the Sun entered the constellation during the Flooding of the Nile, which brought significant amounts of water and fertile soil onto the land. Food security in Egypt depended on this annual natural cycle, a circumstance that also coincided with the arrival of desert lions at the river. Although the lions moved toward the river to avoid the heat and lack of water in the desert at that time, a connection was made by the Egyptians, who honored the lion with festivals, and even today many statues of lions can be found along the course of the Nile River, proof of the reverence with which the ancient Egyptians regarded the desert lions.