Debbie Alber, age 12, of Defoeestville, N.Y., for her question:

WHAT IS THE GEGENSCHEIN?

The gegenschein is related to the zodiacal light, which at least gives us a clue to its where about. We would expect to find it in the zodiac. And the zodiac, of course, is that well traveled heavenly highway that belongs to the sun, the moon and the constellations that change with the season. The gegenschein and the zodiacal light are paler than the Milky Way and both appear in the zodiac.

In our latitudes, we rarely see the ghostly gegenschein. But at certain times of the year, we may see its partner, the zodiacal light. It appears above the horizon before sunrise or after the sun sets, looking like a foggy, cone shape glow, tapering toward the top of the sky. Its pale, pale glow is outdazzled by the moon and by city lights. So to see it, we choose a clear moonless night and go to a remote place.

In March and April, we may see the zodiacal light soon after sunset. The base of its ghostly cone appears on the western horizon, where the sun sank to rest. Its tapering top angles upward along the sun's sloping path, which is in the center of the zodiac.

Early risers get another chance to see the eerie glow in September and October. This time it appears above the eastern horizon, just before dawn. Once again, its tapering cone slopes upward along the sun's path.

In our latitudes, the sun's daily path is a sloping loop over the sky. In the tropics, it climbs almost straight up and down and the noonday sun is almost directly overhead. When we travel to the tropics, we have a better chance to see both the zodiacal light and its ghostly partner, the gegenschein.

There the zodiacal light appears throughout the year, with its tapering cone pointing almost straight up along the sun's path. As it dwindles, it may loop right over the top of the sky. From there it dips down, fanning out to form a pale cone on the opposite horizon. This second hazy light is the counterglow, alias the gegenschein.             Astronomers agree that these partners are hazy sunlight, reflected from swarms of tiny particles. Apparently a vast, thin cloud of superfine fragments reaches out from the sun's equator like a huge, flat plate. From the earth, we sometimes get an oval or edgewise view of it. We see its two hazy halves as the gegenschein and the zodiacal light.