Leo
Leo, the king of the spring sky. It carries Regulus, its chief star riding the ecliptic, and the tale of the Nemean Lion slain by Heracles.
Science
The scienceRegulus, Leo's chief star, is a multiple system of four blue-white giant stars, and because it sits right on the ecliptic (the path the Sun travels), it is often occulted by the Moon and planets. Every year in mid-November the "Leonid meteor shower" rains down from this constellation; its parent is Comet Tempel-Tuttle, which returns on a 33-year cycle. The direction of Leo also holds many distant galaxy groups, making it a "window" for observing external galaxies.
Mythology
How it became a constellationThe first of Heracles' twelve labors was to slay the giant lion that terrorized the valley of Nemea. Because the lion's golden hide could be pierced by no weapon, Heracles fought it bare-handed for thirty days before finally strangling it. He skinned the hide with the beast's own claws and wore it like armor for the rest of his life, and Zeus, to honor his son's feat, set the lion in the sky at the very center of the spring heavens.
Observing Guide
how to observe🔭 How to find it
On a spring evening, look high in the southern sky for a backwards question mark — the "Sickle" — and you have found the lion's head and mane, with the bright star at its base being the lead star Regulus. Imagine the bottom two stars of the Big Dipper's bowl springing a leak, and follow the water dripping southward to arrive at Leo. The star at the tip of the right-triangle tail, off to the east of the Sickle, is Denebola.
✨ What to look for
Beneath the lion's hindquarters (south, between Regulus and Denebola) lies the "Leo Triplet" (M65, M66 and NGC 3628), three bright spiral galaxies gathered close enough to see together in one field of view. To the west, the spiral pair M95 and M96 cluster with the elliptical galaxy M105. All lie more than 30 million light-years away, and the star-poor interior of Leo becomes a window onto these distant galaxies.
📍 Where to see it (US · Canada · UK · Australia)
Leo lies near the celestial equator, so it can be seen from every one of these countries. From the US, Canada and UK it stands high in the southern sky on spring evenings (March–May), with Regulus climbing well up at culmination, then tilts toward the west as June arrives. From Australia it appears the other way up, riding low-to-moderately high in the northern sky through the southern autumn, but is still an easy catch.