Sky Spy

Zodiacal Light

2014-03-27T00:00:00Z 2014-07-03T11:45:45Z Zodiacal LightBy Tim Hunter Special to the Arizona Daily Star Arizona Daily Star

The days are growing longer. The sun sets tonight at 6:40 p.m. and astronomical twilight ends at 8:03 p.m.

This is a good time of year to view the zodiacal light, a large pyramidal glow in the western sky after sunset or in the eastern sky before sunrise.

Look for it in the west on moonless nights 90 minutes to two hours after sunset. It is surprisingly bright and quite large extending at least half-way up the sky from the horizon.

You will need to be out of town and have no city lights in your western sky. Once you have seen the zodiacal light, you will be quite surprised as to how large and bright it is.

The first time you see the zodiacal light you might think it is the glow of city lights. It is actually the glow of microscopic dust particles originating from comets and asteroids. These innumerable fine grains exist along the orbital plane of the solar system.

The sun’s light reflects off them producing a distinct glow best seen during those times when the plane of the solar system is near perpendicular to the eastern or western horizon.

The ecliptic is that part of the sky through which the sun appears to travel over the course of the year. This motion is caused by Earth orbiting around the sun. Earth’s orbital plane is the plane of the ecliptic, and most of the planets lie along this plane within 8 to 9 degrees on either side of it. This region of the sky along the ecliptic is the zodiac. It is where the sun, the moon, and planets travel, and it is the home of the zodiacal light.

Contact Tim Hunter at skyspy@azstarnet.com

Copyright 2014 Arizona Daily Star. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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