Leo is one of the easiest zodiac constellations to spot in the Northern Hemisphere’s spring sky. Its curved “Sickle” of bright stars, shaped like a backward question mark, traces the Lion’s head and mane and gives Leo its most recognizable feature. Look beyond the familiar shape, though, and Leo has plenty more to discover. The constellation is particularly rich in distant galaxies, while the Leonids that radiate from its direction have produced some of the most spectacular meteor storms ever recorded.
Leo Is Best Seen in Spring
For Northern Hemisphere observers, Leo is well placed in the evening from March through May. It can be seen from latitudes between about +90° and −65°, making it visible from much of the Southern Hemisphere as well, where Leo appears during autumn.
Finding Leo in the Night Sky
One of the easiest ways to find Leo is to start with the Big Dipper. Locate Dubhe and Merak, the two stars forming the outer edge of the Dipper’s bowl. These are the famous Pointer Stars: follow them in one direction and they lead toward Polaris, the North Star; extend the line in the opposite direction and it points roughly toward Leo. Look for the distinctive backward-question-mark shape of the Sickle, with bright Regulus at its base.
Leo’s Distinctive Shape and Body
Once you’ve found the Sickle, the rest of Leo is straightforward to trace. Regulus marks the Lion’s heart, while Algieba, the second-brightest star in the Sickle, lies along its curve. Follow Leo eastward from the Sickle and you’ll reach a triangle of stars forming the Lion’s hindquarters and tail. Zosma and Chertan form two corners of this triangle, while Denebola at its eastern end marks the Lion’s tail.
Principal Stars in Leo
Leo’s brightest stars form the outline of the Lion, but several are also interesting stellar systems in their own right.
- Regulus (Alpha Leonis) is Leo’s brightest star, around 79 light-years away, and marks the heart of the Lion at the base of the Sickle. It lies very close to the ecliptic, which means the Moon can occasionally pass in front of it and planets can appear nearby. Regulus is actually a multiple-star system, but its brightest member is remarkable in its own right: it rotates once in roughly 16 hours—so rapidly that it bulges noticeably around its equator rather than being perfectly spherical.
- Denebola (Beta Leonis) lies around 36 light-years away and is one of Leo’s brightest stars. Its name derives from an Arabic phrase meaning “tail of the lion,” matching its position at the eastern end of the constellation. Denebola will also provide a useful starting point for finding the much larger Spring Triangle.
- Algieba (Gamma Leonis) lies in the Sickle and appears to the naked eye as a single golden-yellow point of light. Through a small telescope, however, it resolves into a beautiful pair of giant stars orbiting one another, making Algieba one of Leo’s most rewarding double stars to observe.
- Zosma (Delta Leonis) is a blue-white star around 58 light-years away that marks the Lion’s hip or rump. It forms part of the triangle outlining Leo’s hindquarters and is considerably hotter and more luminous than the Sun.
- Chertan (Theta Leonis) lies around 165 light-years away and forms another corner of Leo’s rear triangle. Although less conspicuous than Regulus or Denebola, it is particularly useful to observers because the Leo Triplet of galaxies lies nearby.
- Adhafera (Zeta Leonis) is a giant star roughly 260 light-years away in the Sickle, where it helps outline the Lion’s mane. Nearby Rasalas (Mu Leonis) marks the upper part of Leo’s head and helps complete the Sickle’s recognizable curve.
Leo also contains a star that you would never guess was special simply by looking at the constellation. Wolf 359 is only about 7.9 light-years away, making it one of the closest stars to our Solar System. Yet this tiny red dwarf is so intrinsically faint that it cannot be seen with the naked eye despite being practically on our stellar doorstep.
The Spring Triangle Links Leo, Boötes and Virgo
Once you’ve traced Leo as far as Denebola, you can use the Lion’s tail to explore a much larger pattern in the spring sky. Denebola forms one corner of the Spring Triangle, together with orange Arcturus, the brightest star in Boötes, and blue-white Spica, the brightest star in Virgo.
The other two stars are easy to find from the Big Dipper, using the familiar saying “arc to Arcturus, then spike to Spica.” Follow the curve of the Dipper’s handle to reach Arcturus, then continue the same sweeping line toward Spica. With both stars identified, Denebola completes a huge triangle linking Leo with two other prominent spring constellations.
Galaxy Hunting in Leo Constellation
Leo is particularly rewarding for galaxy hunters because it lies well away from the bright band of the Milky Way, giving us a relatively unobstructed view into deep space. Several galaxies are bright enough to see with modest telescopes under dark skies, including the famous Leo Triplet.
Start with Chertan, one of the stars marking the Lion’s hindquarters, and look just below it for M65, M66 and NGC 3628. A small telescope can reveal M65 and M66 under a dark sky, while the fainter NGC 3628 is more challenging; a 6- to 8-inch telescope makes the whole group much easier to appreciate. At low magnification, all three can fit into a single field of view.
The three galaxies lie around 30–35 million light-years away and are close enough to one another for their gravity to distort their shapes. M66 shows clear signs of these encounters, while NGC 3628 is seen almost edge-on, so we view its disk from the side rather than face-on, with a prominent lane of dark dust crossing it. M65 appears comparatively undisturbed. Knowing this makes the faint smudges in the eyepiece rather more remarkable: you’re looking at three enormous galaxies interacting millions of light-years away.
Farther west lies Leo’s other major collection, the M96 Group, which includes M95, M96 and M105. Together with M65 and M66 in the Triplet, these give Leo five Messier galaxies, helping make the constellation exceptionally rewarding territory for a telescope on a dark spring night.
The Leonids: When Meteor Showers Become Storms
Every November, usually peaking around November 17–18, Earth passes through a stream of debris that produces the Leonid meteor shower, named because its meteors appear to radiate outward from a point in Leo. However, the meteors themselves are much closer to Earth and have no physical connection with Leo’s stars.
The debris comes from Comet 55P/Tempel-Tuttle, which takes about 33 years to orbit the Sun. Each time the comet returns to the inner Solar System it leaves fresh trails of dust behind, and when Earth encounters particularly dense parts of these trails, the number of Leonids can increase dramatically.
That is what makes the Leonids unusual. Most years they produce a fairly modest meteor shower, but at intervals they can erupt into extraordinary meteor storms. During the great storm of 1966, observers in the western United States saw rates climb to an estimated 40 meteors per second at the peak. In 1833, the famous Leonid storm produced an even more terrifying spectacle, with estimates reaching as many as 100,000 meteors per hour. The display was so overwhelming that some witnesses reportedly believed the end of the world had arrived.
Leo Mythology: The Nemean Lion
The idea of a lion among these stars is much older than the familiar Greek myths. In ancient Mesopotamia, the constellation was already associated with a lion thousands of years ago, making Leo one of the oldest animal figures preserved in the night sky.
In Greek mythology, Leo became identified with the Nemean Lion, the fearsome beast killed by Heracles as the first of his Twelve Labors. The lion’s hide was said to be impervious to ordinary weapons, forcing Heracles to overpower the animal with his bare hands. He later wore its skin as armor, with the lion’s head forming a protective hood.
