Leo is nosing toward the western horizon on these late spring evenings. He's well up in the south and southwest as night falls, with the star Regulus -- the lion's bright "heart" -- leading the way. A curved pattern of stars that outlines Leo's head and mane curls to the upper right of Regulus. Because of its shape, this pattern is called the Sickle.
One of the brightest stars in the Sickle is Gamma Leonis, which is also known as Algieba -- an Arabic name that means "the forehead." It's in the middle of the sickle's curve.
Algieba is really two stars locked in a mutual orbit. But seen through our eyes alone, across a distance of about 130 light-years, the stars blend together into a single yellowish point of light.
William Herschel discovered Algieba's dual identity in 1782. Seen through a small telescope, one of the stars looks yellow-orange, while the other is a little paler. The colors mean that the surfaces of these stars are a good bit cooler than that of our own star, the Sun.
Both of Algieba's stars are old and bloated. They've swelled to many times their original sizes -- much larger than the Sun -- because they've used up most of the nuclear fuel in their cores. Before long, the outer layers of these stars will puff away into space, leaving behind only their hot but dead cores, known as white dwarfs -- depriving the lion of his bright double forehead.
That same fate awaits the Sun -- in several billion years.
Script by Damond Benningfield, Copyright 2011