The Complete Guide to Leo Constellation: Origin, History and Facts

Leo and Leo Minor

Leo is one of the most recognisable signs of the zodiac. In mythology, it is Nemean the Lion, who was slain by the great hero Hercules. Leo is one of the few constellations whose shape and name live up to their name. Unfortunately, however, this is not the case with the near neighbour, Leo Minor.

Almost every culture in the world imagines this constellation as a lion. As one of the 12 tasks of Hercules, Nimean the Lion was killed. The large curved arc on the front side of the constellation forms the famous “Scythe of Leo”. At the base of the constellation is its bright star Regulus, which means ‘little king’ in English. This bright white star is 1.35 magnitudes brighter and 77 light years from Earth. It has two companions moving around it at a considerable distance, the brighter one being visible in a small telescope. Regulus lies almost above the ecliptic, and the Moon and planets occasionally pass in front of it, producing a wonderful occultation.

Unlike Leo, Leo Minor appears fainter and has no distinct shape. Created and added by the Polish astronomer Hewelius in the 17th century.

The Basic Information of Leo Constellation

The definition of Leo Constellation

Leo(♌), the lion, is a large, prominent constellation, the fifth of the zodiac, which dominates the northern spring sky. Leo covers an area of 947square degrees, accounting for 2.3% of the total sky. It ranks 12^th in area among the 88 constellations.

The discovery of Leo Constellation

There has been thousands of years since Leo was found. The commonly accepted story of the naming of Leo is that: in ancient Egypt, more than 4,000 years ago, a lot of lions flocked from the desert to drink water in the Valley of the Nile during the midsummer festival when the sun moved into the Leo sky.

In the ancient Greek astronomer Ptolemy’s list of 48 constellations, Leo Constellation included Leo and Coma Berenices, and Coma Berenices region was associated with the hair on a lion’s tail.  However, in 1602, Danish astronomer Tycho separated Leo and Coma Berenices in his horoscope firstly.

The location and appearance of Leo Constellation

Leo lies between Virgo and Cancer and to the south of Leo Minor and Ursa Major, the north of Hydra, Sextans and Crater. Coma Berenices lies in its west.

Leo is a bright constellation, and easy to spot in the spring sky. Among them, Regulus (α Leo), Al Jabhah (η Leo) , Algieba (γ Leo), Adhafera(ζ Leo), Rasalas (μ Leo) and Ras Elased Australis (ε Leo) form a “sickle” structure from south to north. They represent the lion’s head, neck and mane respectively.

Denebola (β Leo), Arcturus (α Boo) in Bootes and Spica (α Virgo) in Virgo form an equilateral triangle, known as the “Spring Triangle”. These three stars, together with Cor Caroli (α CVn) in Orion has made up the Spring Diamond.

A group of stars that once represented the hair of lion’s tail  has become a separated constellation called Coma Berenices. This constellation contains Wolf 359, which is 7.7 light years from our solar system and is one of the closest stars to Earth.

The stars in Leo Constellation (Stars brighter than magnitude 4.0 )

star	vis mag	abs mag	spectral type	distance (ly)	RA (h m s)	Dec (° ‘ “)
α Leo (Regulus)	1.36	-0.52	B7V	77	10 08 22	+11 58 02
γ Leo (Algieba)	2.01	-0.92	K1IIIbCN+G7IIICN	126	10 19 58	+19 50 30
β Leo (Denebola)	2.14	1.91	A3V	36	11 49 04	+14 34 19
δ Leo (Zosma)	2.56	1.32	A4V	58	11 14 06	+20 31 25
ε Leo (Ras Elased Australis)	2.97	-1.46	G0II	251	09 45 51	+23 46 27
θ Leo (Chort)	3.33	-0.35	A2V	178	11 14 14	+15 25 46
ζ Leo (Adhafera)	3.43	1.02	F0III	99	10 16 41	+23 25 02
η Leo	3.48	-5.60	A0Ib	2,130	10 07 20	+16 45 45
ο Leo(Subra)	3.52	0.43	A5V+F6II	135	09 41 09	+09 53 32
ρ Leo	3.84	-7.38	B1Ib	5,720	10 32 49	+09 18 24
μ Leo (Rassalas)	3.88	0.83	K0IIIbCNCaBa	133	09 52 46	+26 00 25
ι Leo (TszE Tseang)	4.00	2.08	F2IV	79	11 23 55	+10 31 45

There are 96 stars which can be seen by human eyes in Leo, including 52 stars brighter than 5.5 magnitude, in which the brightest one is Regulus (α Leo), whose apparent magnitude is 1.35. It is the 21st brightest star in the whole sky. The primary body of Regulus is a oblate main sequence star, 288 times brighter than the sun, about 79.3 light years from earth, known as the king of the star.

Why is Regulus so bright? It’s actually a multi-star system, with four entities. Regulus A is a blue main sequence star, B is a white dwarf, C is an orange dwarf, and D is a red dwarf. These four stars orbit in pairs. If you look at it with the naked eye, you’ll see only one star, but with binoculars or a small telescope you’ll find a companion.

Algieba (γ Leo) is a double star. According to the combined magnitude of 1.98, it can be said the second brightest star in the Leo Constellation. The apparent magnitude of γ1 is 2.28 and γ2 is 3.51, which are indistinguishable to the naked eye, but can be seen clearly with small telescopes.

Hickson Compact Group 44

The Hickson Compact Group 44 is located in the region between the star Y in Leo and the neck of the lion in the middle of the star. It is a small cluster of four galaxies, 60 million light-years from Earth, which are gravitationally attracted together. The brightest of these are the lateral spiral galaxy NGC 3190 and the elliptical galaxy NGC 3193 both in (top left), which can be seen with a small amateur telescope.

The barred spiral galaxy M95

This small, delicate spiral galaxy is a member of the Leo I Group of galaxies, located half a body length to the south of Leo. It is a very extreme example of a barred spiral galaxy, with the galactic nucleus linking the central bar structure and extending outwards into the spiral arms, and a perinuclear ring around the central nucleus, which is a ring-shaped region of star formation up to 2000 light years in diameter. The Milky Way also appears to have a rod-like structure and is thought to have a similar perinuclear ring.

• Right ascension: 10h44m,
• Declination: +11°42
• Magnitude: 11.4
• Distance to Earth: 38 million light years

NGC 3628

This non-barred spiral galaxy, facing sideways towards us, joins galaxies M65 and M66 to form the Leo Trio group of galaxies. In small telescopes, this galaxy looks like a faint band of light, and in larger units you can see a band of faint dust that is actually the outer edge of the spiral arm, which extends all the way down to the galaxy scale. Although not visible among the magnitude images, there is indeed a tidal tail extending from the side of the galaxy all the way into intergalactic space over 300,000 light years away.

• Right ascension: 11h20m,
• Declination: +13°35
• Magnitude: 9.4
• Distance to Earth: 35 million light-years

The less-than-perfect spiral galaxy M96

The largest and brightest member of the Leo I galaxy group is M96, which is invisible in binoculars and only just discernible in small telescopes. In contrast to its perfect neighbour M95, it has faintly distorted spiral arms, a displaced central nucleus and an asymmetric band of gas dust. It is worth noting that M95 can be seen in front of a more distant cluster of galaxies containing the lateral galaxy in the upper left from the very large telescope of ESO.

• Right ascension: 10h47m,
• Declination: +11°49
• Magnitude: 10.1
• Distance to Earth: 32 million light-years

Twisted and beautiful M66

The most noteworthy galaxy in Leo is M66, the largest and brightest member of the Leo trio, nestled next to the Lion’s hind limb, Leo. At 95,000 light-years across, this galaxy is the same size as the Milky Way and has been distorted by encounters with its galactic neighbours that have caused the galactic disk and spiral arms to distort. Much of the galaxy’s mass is concentrated near the central nucleus, which is apparently still pulled away from the geometric centre of the spiral arm.

• Right ascension: 11h20m,
• Declination: +13°00
• Magnitude: 8.9
• Distance to Earth: 35 million light years

Some interesting galaxies in Leo Constellation

There is a wealth of galaxies to observe in Leo, starting with the Leo triplet, which has three galaxies (NGC3628, M66 and M65). They can be in the field of view of a small telescope. They’re all large spiral galaxies, but they look different because they’re at different angles from Earth.

The other Messier objects in Leo are M95, M96 and M105. M95 and M96 are a pair of spiral galaxies with long, cloud-like shapes visible with small telescopes.

Leonids

The Leonids is an annual meteor shower that reaches its maximum on November 17 and 18. There exists a radiant point in Leo, which is near the center of the Sickle asterism. The shower provides modest displays in most years but spectacular meteor storms every 33 years.

Finnish meteor expert Esko Lyytinen and Markku Nissinen predicted how the Leonids would behave during the next three returns of its parent comet Tempel-Tuttle (in 2031, 2065 and 2098) in the late 2004. Previously, David Asher and Robert McNaught had mentioned similar point in their IMO Yearbook published in 1999. Between 2033 and 2034, there will be 3-5 encounters with the earth. The parent comet will return to its circa 1900 orbit around 2098, which is why most people think the next storm is likely to occur around 2098. Of course, we will meet enough of them in both 2031 and 2065.

How to find and where can you see Leo Constellation

Latitudes between 82° N and 57° S have a chance to see Leo in its entirety. Leo rises at midnight on March 1 each year. For observers in the northern hemisphere’s mid-latitudes, Leo will be visible from the middle of winter to late spring, but the best month to see it is April.

How can we find Leo in sky? We have two ways. Firstly, we will find the Spring Triangle, then find Arcturus and Spica to make a isosceles triangle by using the light of the Big Dipper. Therefore, we can locate the Denebola, the tail of the Leo, whose east is a group of stars of Leo. Another way is to use the Phecda, the third star of the Big Dipper. Extend about 10 times in the direction of the North Star from Phecda, we will find the Regulus.

Mythology about Leo Constellation

The origin of Leo is related to Hercules.

Hercules was the illegitimate son of Zeus and a mortal. He was born with unmatchable divine power, which made Hera burn with jealousy. When Hercules was still a baby, Hera put two giant snakes in his cradle, hoping to bite Hercules to death. To her surprise, Hercules smiled and held them to death. Therefore, Hercules was regarded as “the greatest hero of mankind” since he was young.

Hera, of course, would not give up killing Heracles just for one failure. She intentionally let Heracles mad and beat his own wife. This made Hercules regret and sad after he woke up. Later he decided to penance to clear his iniquity. He came to Mycenae and asked the king for tasks. However, the king was directed by Hera, and gave him twelve tasks beyond the bounds of difficulty, which had to be done in 12 days, especially one of which was to kill a man-eating lion.

This lion usually lived in the forest, so Hercules went into the forest to look for it, but the forest was silent: all the animals, birds, deer, squirrels were eaten by the lion. Hercules dozed off because he was tired of looking for the lion. At that moment, the man-eating lion emerged from a cave with a double opening. Hercules quickly  opened his eyes and saw that the lion was five times the size of a normal lion and covered with animal blood, which was horrific. Hercules shot him with arrows and beat him with sticks, but it was of no use. The lion was invulnerable. Finally Hercules fought with the lion at hand-to-hand and eventually strangled the lion with brute force.

Although the man-eating lion died, Hera threw the dead lion into the air and it became a Leo constellation.

Etymology of Leo Constellation

Firstly, the early Hindu astronomers named it Asleha or Sinha. But later, according to the influence of Greece and Rome, Romans generally called it Leya or Loin, which is from the word Leo.

Although the name has the same meaning of the lion, people from different countries have different appellations of the Leo constellation. For example, the Persians called it Ser or Shir; the Turks called it Artan and the Jewish people called it Arye.   

Ovid wrote it as Herculeus Leo and Violentus Leo which was related to the mythology of the Leo constellation. God always identified with the lion while a lion’s skin was his frequent dress. However, Manilius called it Jovis or Junonis Sidus (Star of Jove and Juno) with the consideration of its emperor nature.

Astrology of Leo Constellation

Leo is one of the Fire Signs (others are Aries and Sagittarius), and also one of the Fixed Signs (together with Taurus, Scorpio and Aquarius).

Once, Nechepso, the Egyptian pharaoh and his priest Petosiris said that sun rose near Denebola at the creation of the world. Hence, Leo was Domicilium Solis, which symbolized fire and heat, called “House of the Sun”.

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