Tell Me About Leo, the Lion

Leo, if you're of an astrological bent*, is the fifth sign of the zodiac: if you were born between July 23rd and August 22nd its your sign. We're not here for superstition, though, so let's find out about the asterism known as Leo.

How to find it

The Plough (part of Ursa Major) is a really useful asterism to use for finding others because of its relatively simple simple yet distinctive shape making it easy to find. Use it to find Leo as follows:

Finding Leo by T. Briggs is licensed under CC BY-NC-SA 4.0

If you think of this portion of Ursa Major as looking like a saucepan, the two stars forming the side of the pan opposite to the handle are often called the "pointer" stars. That's because they point at things. In the context of this post, they're pointing at Leo, which is in the direction indicated, at around 5-6 times the distance between the pointer stars.

The Stars in Leo

The Stars in Leo by T. Briggs is licensed under CC BY-NC-SA 4.0

The main asterism Leo is made up of 9 stars, labelled in the image above. A bit about each:

α Leonis (Regulus)

Regulus, like so many stars it's actually a quadruple star system. The main star is a blue-white main-sequence star that is 77.5 light years from Earth. The system is the brightest "star" in Leo, and one of the brightest in the night sky. The system is more than a billion years old.

β Leonis (Denebola)

Denebola (meaning "the lion's tail"), the second-brightest solo star in the constellation, is 75% more massive than our Sun, and around 15 times brighter. It's about 36 light years away from us and is relatively young, at only 400 million years old.

γ Leonis (Algieba)

Algieba ("the forehead"), is a binary star system with a gold-yellow giant primary star. Together they appear brighter than beta Leonis, but the primary on its own is the third brightest star in the constellation. The two stars of Gamma Leonis orbit each other once every 600 years and are around 126 light years from Earth.

δ Leonis (Zosma)

Zosma ("girdle", in ancient Greek) is estimated to be about 700 million years old and around 58 light years away from us. It's about twice the mass of the Sun, 15 times as bright, and rotates rapidly enough to produce a bulge around its equator.

ε Leonis (Algenubi)

Algenubi ("the southern star of the lion's head") is 162 million years old and about 250 light years away. It's about 4 times as massive as the Sun, and getting on for 300 times as bright.

ζ Leonis (Adhafera)

Adhafera, is about 274 light years away from the Sun and is one component of an optical double. Although still visible to the naked eye it is relatively faint.

η Leonis (Al'Dzhabkhakh)

Eta Leo is a white supergiant star about 10 times the mass of the Sun, and 19 thousand times as bright. It's about 25 million years old, and 1,270 light years away.

θ Leonis (Chertan)

Chertan ("two small ribs") is one of the brighter stars in Leo and is about 165 light years away from us and 550 million years old. 

μ Leonis (Rasalas)

Rasalas is an evolved giant star that is about 1.5 times the Sun's mass but has expanded to around 14 times its diameter. It's about 3.35 billion years old and shines 63 times brighter than the Sun.

Bonus Objects

The Leo Triplet

Known as the M66 Group, this is a triple-whammy consisting of M65 (a spiral galaxy about 35 million light years away), M66 (another spiral galaxy, about 31 million light years away) and NGC 3628 (also known as "the Hamburger Galaxy" about 35 million light years away). It's not visible to the naked eye

*I'm not, just to be clear


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