Zodiacal Light in the Evening

Zodiacal Light in the Evening

Have you ever seen the zodiacal light? This huge pearly pyramid is on its best display in the Northern Hemisphere on moonless evenings from February through April. All you need is a location far from artificial lights (at least 40 miles from a small city and 80 miles from a major metropolis) that also has an unobstructed western horizon.

Go out an hour after sunset and look to the west. Even though the Sun is now far below the horizon, a huge dome of light marks the spot where it disappeared. As this light fades and shrinks down to the horizon, another glow will be unmasked; a tall, leftward-slanting pyramid of light. It follows the path of ecliptic, running left of Aries and then between the Hyades and Pleaides, the sky's most spectacular star clusters.

Aside from its shape, you might think it was just part of the twilight, but it will linger long after the rest of the sky is fully dark. The first time I saw the zodiacal light, I thought it was light pollution, but light pollution forms a low band along the horizon. It's amazingly brighter — even brighter than the Milky Way — and once you've seen it, you'll never again have trouble recognizing it.

What are you seeing? The zodiacal light is the combined glow of countless tiny particles (debris from comets and asteroid collisions) that orbit the Sun.