Zodiacal Light

Last updated on September 16, 2023

The Phenomenon of Zodiacal Light: A Celestial Spectacle

Zodiacal light, also known as the "false dawn," is a captivating natural phenomenon that occurs after sunset or before dawn. It appears as a soft cone of light stretching upwards from the horizon. This ethereal glow is actually sunlight scattered by countless dust particles that extend outward in the plane of the Solar System, possibly even reaching beyond Jupiter. While it is most visible in or near the tropics where the skies are darker and the ecliptic is strongly inclined to the horizon, recent images have shown that it can also be observed in more northerly and light-polluted regions like Europe.

Unveiling the Elusive Zodiacal Light

The Zodiacal Light is a remarkable celestial feature that remains unseen by many. However, it is the largest feature in the solar system that can be observed with the naked eye. It is unfortunate that something so commonplace has become a challenge for most people due to the impact of human activity on our skies. Nevertheless, understanding the best conditions for viewing this natural wonder can greatly increase the chances of experiencing its splendor.

Optimal Viewing Conditions

The visibility of Zodiacal Light greatly depends on the time of year and latitude. Under favorable conditions, this phenomenon can surprise observers with its brightness, earning it the moniker "False Dawn." In order to make the Zodiacal Light more apparent, a dark horizon is essential as it reveals the broader and brighter regions lower down. Although long-exposure photographs may capture more stars than the naked eye can discern, our eyes are remarkably adept at detecting diffuse glows like the Zodiacal Light.

The Best Time to Observe Zodiacal Light

The best time to witness Zodiacal Light in the evening from the UK or middle to north Europe is during February and early March. Contrary to popular belief, this phenomenon is not limited to the spring equinox. In fact, it can be observed as early as mid-January. However, if you wait until after the equinox, the Zodiacal Light may extend into the Milky Way, making it more challenging to distinguish.

For early risers, the pre-dawn hours from mid-September to late November offer the best viewing opportunities. Prior to the autumn equinox, when the Milky Way tends to interfere, the Zodiacal Light can be more easily observed. However, it is important to plan your observation carefully, selecting times when the Gegenschein—the faint glow opposite the Sun—appears high in the sky and is not obscured by the moon or bright stars, planets, or the Milky Way.

Seeking Out Zodiacal Light

If you are eager to catch a glimpse of Zodiacal Light, the next sighting opportunities will occur from March 2nd onwards when the moon no longer brightens the sky. Look towards the south-west after sunset and ensure that the sky has fully darkened. Due to its vast cone of light, using averted vision and gently swaying your head from side to side can help make this celestial phenomenon more apparent.

In conclusion, Zodiacal Light offers a mesmerizing spectacle that deserves greater recognition and appreciation. By understanding the optimal viewing conditions and planning your observations accordingly, you can unlock the beauty of this natural phenomenon. So take a moment to gaze at the heavens and embark on a celestial journey to witness the ethereal glow of Zodiacal Light.

Now is the time!

Upper image - Zodiacal light from Europe. Taken in Wiltshire, England on 14th February by Richard Fleet webmaster of Glows Bows & Haloes. 60s unguided exposure at f/4 ISO 1600, Canon 20D, Sigma 10-20mm lens at 10mm. Unprocessed JPG.

Lower image - On the same night by Claudia Hinz (Atmospheric optics site) from high on Mount Wendelstein in the Bavarian Alps, Germany. Unguided exposure.

Images © the photographers, shown with permission.

The zodiacal light is a soft cone of light stretching upwards from the horizon after sunset or before dawn when it is sometimes called the 'false dawn'. It is sunlight scattered by a disk of innumerable dust particles extending outwards in the plane of the Solar System to Jupiter and perhaps beyond.

The light is faint and is best seen in or near the tropics when skies are dark and the ecliptic - where it is concentrated - is strongly inclined to the horizon.

Is there hope of seeing it in more northerly and light polluted Europe? These images show that there is.

Richard Fleet gives these tips. �The Zodiacal Light is the largest feature in the solar system visible to the naked eye and yet most people have never seen it. From less developed parts of the world it is all part of the normal pattern of changing light between night and day and is easily taken for granted. It says a great deal about what we've done to our skies that something so commonplace should be regarded as a challenge for most people.

Time of year and latitude makes a huge difference to how visible it is. Under really favourable conditions it can be surprisingly bright, �False Dawn� isn't a bad name for it and you can tell the dawn is coming hours before the sky gets light.

What really makes it obvious is having a dark horizon so that you see the broader and brighter regions lower down. That shows up well on Chris Brown's earlier OPOD but is completely lost in sky glow on mine. Of course the 60 second exposure shows rather more stars than you would see with the naked eye, but the eye is remarkably good at picking out diffuse glows like this.

This is the best time of year (February/early March) to see it in the evening from the UK or middle to north Europe. Some people think it is only visible around the spring equinox because then the ecliptic is at its steepest, but any time from mid January is good for us. If you leave it until after the equinox the ZL extends into the Milky Way and gets lost.

For early risers the best times for the pre-dawn view are from mid September to late November, before the autumn equinox the Milky Way tends to be a nuisance.

Now the Gegenschein really is a challenge! I have seen it from Wales and a number of times from Africa. That needs careful planning to choose times when it is high, when there is no moon and there are no bright stars, planets or Milky Way anywhere nearby.�

The next sighting opportunities will be from March 2nd onwards when the moon no longer brightens the sky. Look in the south west after sunset and when the sky has fully darkened. Remember that the cone of light is huge. Use averted vision and swing your head from side to side - that way it can become more apparent. Can you find it?

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Reference Atmospheric Optics

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