Leo constellation
Leo (the Lion) is a constellation in the northern sky, best seen in the evening in April. Its brightest star is Regulus (magnitude 1.35). It contains the Sickle. Leo covers 947 square degrees and is the 12th-largest of the 88 constellations.
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How to find Leo, step by step
Let the Big Dipper "leak" onto the lion.
- On spring evenings find the Big Dipper high in the north.
- Draw a line from Megrez through Phecda, the two stars of the bowl nearest the handle, and continue south: it leads to Regulus.
- Regulus is the dot of a backward question mark, the Sickle, which forms Leo's head and mane. East of it a triangle of stars ending in Denebola marks the lion's hindquarters.
Detailed star map of Leo
Facts
| Latin name | Leo (genitive: Leonis) |
|---|---|
| Abbreviation | Leo |
| Meaning | the Lion |
| Area | 947 square degrees (12th of 88) |
| Location | right ascension 10.7 h, declination +15° |
| Visible from | latitudes 83° N to 57° S (whole constellation) |
| Best month | April (at about 9 pm) |
| Brightest star | Regulus |
| Stars brighter than magnitude 6 | 81 |
| Named stars (IAU) | 9 |
| Messier objects | M65, M66, M95, M96, M105 |
| Neighbors | Cancer, Coma Berenices, Crater, Hydra, Leo Minor, Sextans, Ursa Major, Virgo |
How to find Leo
From 40° N (the USA, southern Europe, Japan) look south in April evenings: at about 9 pm Leo stands highest, around 65° above the southern horizon. From 35° S (Australia, South Africa, Argentina) it is highest in the north, about 40° above the horizon. The months before and after (March and May) are also good: then it is up a couple of hours earlier or later.
Leo borders Cancer, Coma Berenices, Crater, Hydra, Leo Minor, Sextans, Ursa Major and Virgo.
Asterisms with stars in Leo: Spring Triangle, Sickle of Leo.
Stars of Leo
Leo has 81 stars brighter than magnitude 6, the limit of the naked eye under a dark sky. These are the brightest:
| Star | Designation | Magnitude | Type | Distance |
|---|---|---|---|---|
| Regulus | α Leonis | 1.35 | B7V | 77 ly |
| Denebola | β Leonis | 2.14 | A3V | 36 ly |
| Zosma | δ Leonis | 2.56 | A4V | 58 ly |
| Algieba | γ1 Leonis | 2.61 | K1-IIIbFe-0.5 | 126 ly |
| — | ε Leonis | 2.98 | G1II | — |
| Chertan | θ Leonis | 3.34 | A2V | 176 ly |
| Adhafera | ζ Leonis | 3.44 | F0III | 239 ly |
| Subra | ο Leonis | 3.52 | F6II+A1-5V | 135 ly |
| — | η Leonis | 3.52 | A0Ib | — |
| — | γ2 Leonis | 3.8 | G7IIIFe-1 | — |
| — | ρ Leonis | 3.85 | B1Ib | — |
| Rasalas | μ Leonis | 3.88 | K2IIICN1Ca1 | 124 ly |
Deep-sky objects in Leo
Leo contains 5 objects from Charles Messier's catalog:
- Messier 65 (M65): spiral galaxy, 9.3 mag
- Messier 66 (M66): spiral galaxy, 8.9 mag
- Messier 95 (M95): spiral galaxy, 9.7 mag
- Messier 96 (M96): spiral galaxy, 9.3 mag
- Messier 105 (M105): elliptical galaxy, 9.8 mag
Printable Leo map and outline
A black and white version for printing and a plain outline of the Leo figure, useful for school projects, worksheets and learning to recognize the shape.
History
Leo is one of the 48 constellations listed by Ptolemy in the Almagest (2nd century AD). Its official boundary was drawn by Eugène Delporte for the International Astronomical Union in 1930.
Questions about Leo
What is the brightest star in Leo?
Regulus, at magnitude 1.35, about 77 light-years away.
When can you see Leo?
Leo is best seen in the evening in April. The whole constellation is visible from latitudes between 83° N and 57° S.
How many stars are in Leo?
81 stars in Leo are brighter than magnitude 6 and can be seen with the naked eye under a dark sky; 9 of them have official IAU names.
What does Leo mean?
Leo means “the Lion” in Latin. Its abbreviation is Leo and the genitive, used in star names such as α Leonis, is Leonis.
