Image from NASA APOD! ZODIAC LIGHT.
The zodiac light takes its name from the ancient band of 12 constellations through which the sun, moon, and planets pass, the Zodiac. Modern astronomers prefer to use the name of the sun’s path, the Ecliptic, and add a 13th constellation, Ophiuchus.
Most of the material in the solar system is concentrated in a flat disk coinciding with the ecliptic. Besides the eight planets and their accompanying moons, there are thousands of asteroids and millions of smaller particles, ranging all the way down to fine grains of interplanetary dust. These millions of particles cannot be seen as individual objects, but like the distant stars in the Milky Way, their tiny inputs of light combine to create a faint glow along the plane of the ecliptic. This is what we call the zodiacal light.
Tips & Tricks to see Zodiac light:
Most people nowadays have never seen the Milky Way because its light is so faint that it is wiped out by light pollution except under dark country skies. The zodiacal light is even fainter than the Milky Way. So to see the zodiacal light you first of all need to get away from light polluted urban skies. You need to give your eyes at least 20 minutes in total darkness so that they reach their maximum sensitivity. You also need to observe at the dark of the moon, i.e during its crescent phase or new moon. Finally you have to choose the right time of the year, when the ecliptic is close to rising vertically in the sky, normally during equinoxes both in Northern & Southern hemispheres. But, of course, spring and autumn equinoxes fall in different months for Earth’s Northern and Southern Hemispheres. So if you’re in the Northern Hemisphere look for the zodiacal light before dawn(sunrise) from about late August through early November. In those same months, if you’re in the Southern Hemisphere, look for the light in the evening after dusk(sunset). Likewise, if you’re in the Northern Hemisphere, look for the evening zodiacal light after sunset from late February through early May. During those months, from the Southern Hemisphere, look for the light in the morning before sunrise.
It will also help to use what astronomers call “averted vision.” This takes advantage of the fact that the most sensitive cells in our eyes’ retinas are not in the central part of the visual field, but slightly away from it. The trick is to look slightly away from where you expect the zodiacal light to appear. This will put it on the most sensitive part of your eye, and improve your chance of seeing it.
Once you manage to spot the zodiacal light, try to follow it upward in the sky towards the zenith. You may see a faint glow directly opposite the sun’s location, called the gegenschein, German for “counterglow.” This is a slight concentration of sunlight reflected off the interplanetary dust, just as traffic signs reflect back the light of car headlights. Spotting the zodiacal light and gegenschein are among the rarest astronomical observations any stargazer can accomplish. Good luck, and let us know if you succeed.