2022 Zodiacal light


It's that time of year when we get to see the evening Zodiacal light. This is a huge softly radiant pyramid of white light with its base near the horizon that stands almost straight up in the dark sky this time of year.

Zodiacal light is sunlight reflecting of dust particles left by comets and asteroids that move in the same plane as Earth's orbit around the Sun. It becomes visible about ½ hour after evening twilight when we can no longer see the Sun, but its light reflects off the dust.

As you know, twilight is the time of day between daylight and darkness. The Sun is below the horizon, but its rays are scattered by small particles in earth's atmosphere to create the colors of twilight which are often pinkish. 

Basically, when the Sun is 6 degrees below the horizon it's dark enough for streetlights to come on.  When it's 18 degrees below the horizon the sky is dark enough for stars to appear in the sky.

The Zodiacal light stands up so straight because the ecliptic that the Sun, moon, and planets travel along, is almost straight up this time of year.  It only leans slightly to the left. That's why the moon is currently so high in the sky. The best time to view it is when the moon is not in the sky, which will be in the evening of Feb. 1 when the new moon occurs. But it will be quiet for a few nights after that. The full moon is on the 16th, but then after that it will rise later making the sky dark for a while.

When sunlight shines through Earth's atmosphere the light looks pink. But when it reflects off dust particles not in our atmosphere, the light is white. So, when we see the zodiacal light, we're looking edgewise into the plane of our solar system. The light is brightest when it's closer to the Sun, which is why early evening provides the best viewing.

So moonless evenings in February, March and April are the time to go out and look for the Zodiacal light. Look in the south-west where the Sun sets about a half-hour after sunset, basically shortly after the sky gets completely dark. Since the current sunset is at 5:30, I would start looking at 6 p.m. This pyramid of light will extend one third to halfway up in the sky.

It'll be visible for 20-30 minutes while it gradually gets brighter and then dimmer. While you're looking at it, please understand that a large part of our planet can't see it because of light pollution. We are very fortunate to have the clear skies that we do.  So, let's protect this wonderful treasure that we have.