WRAL WeatherCenter Blog

Look for zodiacal light in September sunrises

Posted September 5

In this 30 second exposure, a meteor streaks across the sky during the annual Perseid meteor shower Friday, Aug. 12, 2016 in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)

— September brings the beginning of meteorological fall in the northern hemisphere, but it's also the beginning of the zodiacal light season.

The zodiacal light is a very faint, very diffuse triangle of light that can be seen along the eastern horizon just before morning twilight. Also known as false dawn, this phenomenon can be seen during the weeks surrounding the equinox, now through mid-October.

Look for it again in the spring in western skies after evening twilight.

In rural, darker locations that are free from light pollution, zodiacal light can extend across the sky as a faint band from horizon to horizon. The zodiacal name comes from that location in the sky.

The band of light was previously thought to be caused by light scattering in the upper atmosphere. Today we know it to be caused by sunlight reflecting off small dust particles in space.

These sand size dust grains are the leftovers from the formation of the Earth and other solar system planets 4.5 billion years ago.

The name comes from the path the light takes through the zodiacal constellations of Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius and Sagittarius.

These constellations hold a special place in the sky, not because of astrological significance, but because of a very real astronomical one. This is the ecliptic line or the path of the the sun each of the planets of the solar system takes through the sky each day. The dust that creates the zodiacal light follows the same roughly flat orbital plane as the planets.

Look for zodiacal light about 30 minutes before sunrise through mid-October.

Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.

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