Leo Constellation Guide: Finding Regulus and Galaxies

Leo is one of those rare constellations that actually looks like what it's supposed to represent. The distinctive Sickle asterism, a backward question mark of stars, forms the lion's head and mane, while a triangle of stars to the east marks the hindquarters. It's one of the easiest constellations to spot in the spring sky, and once you've found it, you're sitting on top of some excellent galaxy hunting.

Finding Leo

Leo dominates the southern sky from March through June. Here's how to find it:

1. Start with the Big Dipper, which is high overhead in spring.
2. Find the two "pointer" stars on the bottom of the Dipper's bowl (Merak and Dubhe). These normally point toward Polaris in one direction.
3. Now go the opposite direction from Polaris, southward, and you'll run into Regulus, the brightest star in Leo.
4. Alternatively, use the phrase "arc to Arcturus, spike to Spica" starting from the Dipper's handle, and Leo sits between the Dipper and Arcturus.

Regulus (Alpha Leonis) is a blue-white star of magnitude +1.4, making it the 21st brightest star in the sky. It sits almost exactly on the ecliptic, the path the Sun, Moon, and planets follow across the sky, so you'll frequently see planets passing close to or even occulting Regulus.

The Sickle: Leo's Head and Mane

The Sickle (or backward question mark) is the most recognizable part of Leo. It traces the lion's head, with Regulus at the base (the dot of the question mark) and the curve sweeping up through Eta Leonis, Gamma Leonis (Algieba), Zeta Leonis, Mu Leonis, and Epsilon Leonis.

Algieba (Gamma Leonis) deserves special attention. Through a telescope at 80x or more, it resolves into a beautiful double star, two golden-orange stars of magnitudes +2.2 and +3.5, separated by about 4.4 arcseconds. It's one of the finest double stars in the sky and a favorite among visual observers.

Galaxy Hunting in Leo

Spring is galaxy season, and Leo sits in one of the richest regions for galaxy observing. The reason? In spring, we're looking away from the plane of the Milky Way, which means the dust and stars of our own galaxy don't obscure the view of distant galaxies beyond.

The Leo Triplet (M65, M66, NGC 3628)

The crown jewels of Leo's galaxies are the Leo Triplet, three galaxies that fit in the same telescope field of view:

• M65: A tightly wound spiral galaxy seen at a moderate angle. It appears as an elongated oval glow with a bright core. Magnitude +10.3.
• M66: A slightly brighter spiral with more visible structure. Asymmetric arms give it character in photographs. Magnitude +9.7.
• NGC 3628: An edge-on spiral with a prominent dark dust lane bisecting its disk. Sometimes called the "Hamburger Galaxy." Magnitude +10.2, fainter and more challenging than its companions.

To find the Leo Triplet, look about halfway between the stars Theta Leonis (Chertan) and Iota Leonis. An 8-inch telescope under reasonably dark skies will show all three galaxies in a single low-power field, a genuinely thrilling sight.

More Leo Galaxies

Beyond the triplet, Leo offers several more galaxies worth hunting:

• M95 and M96: A pair of galaxies about 3° east of the star Rho Leonis. M96 is slightly brighter at magnitude +10.1. Both are visible in 6-inch telescopes.
• M105: An elliptical galaxy near M96, forming a small galaxy group. Appears as a round, bright glow.
• NGC 2903: Often overlooked but one of the finest galaxies in Leo, a barred spiral at magnitude +9.7. It's bright enough to spot in binoculars from a dark site and shows considerable detail in 10-inch+ telescopes.

Best Viewing Conditions

Leo is optimally placed for observing from March through early June. For galaxy hunting specifically, you want:

• A moonless night, galaxies are faint, extended objects that wash out easily in moonlight.
• Dark skies, the darker your site, the more galaxies you'll see and the more detail you'll detect.
• Steady seeing, less critical for galaxies than for planets, but it still helps with resolving fine structure.

Check our what's visible tonight page to find when Leo is best positioned for your location, and our telescope guide if you're gearing up for spring galaxy season.