The constellation of Leo represents the lion killed by Hercules (who is currently chasing the lion across the sky) as one of his twelve tasks in Greek mythology. However, the constellation is very ancient and was first created because the lion was the king of all the beasts. The name of its main star Regulus means “little king” in Latin, and was called “king” by the Babylonians. Regulus is a very young star, which is 3.5 times the mass of our Sun. It rotates very rapidly – its rotation period is 16 hours compared with the Sun’s 27 days – which means it is egg-shaped rather than spherical. Leo is an easy constellation to make out, as its shape looks like the statue of a sphinx in the Egyptian desert; the front end of this sphinx is an asterism called the Sickle.  .

Leo contains many fine galaxies, but there are no star clusters or planetary nebulae, which means there is nothing to see with binoculars or a small telescope. The most famous sight in Leo is the Leo Triplet [1] of bright spiral galaxies, Messier 65, Messier 66 and NGC 3628 – a galaxy which is seen edge-on and is called the Hamburger Galaxy because of its appearance. They are all close to each other in space, being about 35 million light years away. You will need to be in a dark area with a fairly large telescope to observe them.

There are, however, two double stars worth observing in Leo. The best is Algieba (Gamma Leonis). Its stars are bright and golden-tinted; an appropriate colour for a double in the lion’s mane. The two stars are close together, so you will need to use a high magnification. 54 Leonis, above the body of the lion – which can be spotted with the naked eye – is a yellow and blue double in a telescope.