THE SKY GUIDE CHALLENGE
Can you spot the ethereal and elusive Zodiacal Light in March’s evening skies?
The Zodiacal Light isn’t a commonly observed phenomenon from the UK. We don’t often have the darkness that’s required to see it and it’s not always obvious even when it’s there, appearing large, faint and subtle.
Its origin is thought to be from short-period ‘Jupiter-family’ comets. The tiny particles of comet dust released from these objects orbit in the plane of the Solar System. When sunlight interacts with the 10–300-micron-sized particles, from Earth we sometimes see its presence after sunset or before sunrise. A high ecliptic angle with the prevailing horizon is preferable for spotting the Zodiacal Light, and during March that ecliptic angle is optimal after the Sun has set, when it’s the western horizon that is important. Conversely, for pre-dawn appearances the optimal place and time is the eastern horizon around late September.
In order to see this ghostly glow, there are several factors that need to align. Dark skies are a must. If you live in a lightpolluted area, as most of us sadly do, you may need to travel elsewhere. Natural light pollution should be avoided too, so time any attempts for when the Moon is out of the way. In the spring this will typically be when it’s in the waning gibbous phase through to the very earliest of the waxing crescents. For the next period, the optimal date ranges are 12–23 March and 9–22 April. The weather needs to be good too, with a clear, crisp spring sky. High, hazy cloud will act as a perfect filter for the Zodiacal Light, so watch out for this too.
When visible, the Zodiacal Light presents itself with a distinctive conic shape. The cone’s vertical axis is tilted relative to the horizon, running along the ecliptic with the lower edges of the cone bulging outward. The best time to try to see the Zodiacal Light is during the 90-minute window that starts 90 minutes after sunset. For a directional guide, follow the line of the planets, an imaginary line from Venus through to Mars conveniently defining the line of the ecliptic for you.
If you fail to see the Zodiacal Light visually, a wide-angle camera pointed in the directions mentioned above at the correct times may fare better. The camera should be set to produce a relatively deep but not overexposed sky, and doesn’t need to track, a fixed tripod being fine.
A time-lapse sequence can be useful here because it can be played back to show whether the characteristic Zodiacal Light shape was really present, even if you couldn’t see it visually. Don’t forget to let us know if you do manage to see or photograph it.
To see this ghostly glow, dark skies are a must so you may need to travel