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Zodiacal Light – false dawn

It’s back! The zodiacal light is practically a sign of spring as it  pokes up in the western sky like a ghost awoken. Keen sky-watchers can see this ‘false dawn’, the most elusive astronomical phenomena – the zodiacal light, starting February 2nd, about an hour after sunset, and for the two weeks that follow.

This pyramid-shaped light is easily mistaken for the glow from a far-off city just over the horizon, and it is sometimes called the false dawn. But this ethereal light is actually caused by sunlight reflecting off ancient dust suspended between the planets. The best time to catch the ghostly sky light is about an hour after sunset, looking toward the western horizon from a dark region with low light pollution.

Sunlight reflecting off comet and asteroid dust concentrated in the plane of the Solar System creates the zodiacal light. Heat from the Sun vaporizes dust-laden comet ices, which expand outward to form the comet’s coma. Some of the material gets blown back by the pressure of sunlight into a tail which diffuses along the comet’s orbit to live a second life as the zodiacal light. Dust from asteroid collisions also contributes a significant fraction to the mix. Much of it settles in the plane of the Solar System, scattering sunlight like clouds of dust raised by running horses.

How to find it:

  • Easier to see as you get closer to Earth’s equator.
  • Can be glimpsed from northerly latitudes.
  • Look in a south-western direction.
  • Occurs when the Moon makes itself scarce.
  • Time: 90 minutes after sundown and lasts about an hour and a half.
  • Is visible in clear dark skies.
  • The light looks like a hazy pyramid.
  • It’s comparable in brightness to the Milky Way, but even milkier in appearance.


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