The zodiacal light appears as a soft triangular glow after sunset, caused by sunlight reflecting off interplanetary dust.
Credit : Mindaugas Gaspa, Shutterstock
As winter draws to a close, some people notice something unusual after sunset: a faint, triangular glow rising from the horizon. It’s not the Milky Way. It’s not lingering sunset light. And it’s certainly not an aurora. What you’re actually seeing is the zodiacal light – one of the most overlooked sights in our solar system.
In the weeks around the spring equinox, this soft cone of light becomes easier to spot in the Northern Hemisphere. And if you know where to look, you can see it with the naked eye.
What is the zodiacal light and why does it appear?
At first glance, the zodiacal light looks like a pale beam stretching upwards from where the Sun has just set. Astronomers sometimes call it a “false dusk” or “false dawn” because it mimics the glow of twilight.
In reality, it has nothing to do with Earth’s atmosphere. The glow comes from sunlight reflecting off a vast cloud of interplanetary dust spread across the plane of our solar system.
These particles are tiny – often compared to smoke from a cigarette – and are believed to be debris left behind by comets and asteroid collisions. They sit along the ecliptic, the same path the Sun appears to follow across the constellations of the zodiac. That’s where the name comes from.
Interestingly, research linked to NASA’s Juno mission has suggested that some of this dust could even originate from Mars. As Juno travelled towards Jupiter, it measured dense regions of interplanetary dust between Earth’s orbit and the asteroid belt. Scientists are still trying to understand how Martian dust could escape the planet’s gravity and drift into space.
When is the best time to see the zodiacal light in Europe?
The best viewing window comes in the weeks around the spring and autumn equinoxes, when the angle of the ecliptic makes the glow stand out more clearly.
At the end of winter in the Northern Hemisphere, the zodiacal light is visible in the evening, shortly after sunset. In the Southern Hemisphere, it tends to appear before dawn.
Astronomers explain that during this period, the ecliptic is positioned almost vertically relative to the horizon. That alignment reduces interference from other light sources and places the glow in a darker part of the sky, away from the Milky Way.
How to spot the zodiacal light from Spain and across Europe
You don’t need a telescope. But you do need darkness.
To see it clearly, head somewhere well away from city lights with an unobstructed view of the western horizon. Around 90 minutes to two hours after sunset, look towards where the Sun disappeared. On a clear night, you may notice a faint triangular glow stretching upwards.
In autumn, the best time shifts to the early morning hours before sunrise, when you should look east instead.
One common mistake is confusing the zodiacal light with the Milky Way. The difference? The Milky Way has a grainy, speckled appearance because it’s made up of distant stars. The zodiacal light, by contrast, looks smooth and diffuse, more like a gentle wash of light.
A quiet spectacle in the solar system
The zodiacal light isn’t dramatic like a meteor shower or a total eclipse. It’s subtle, almost easy to miss. But that’s part of its charm.
What you’re seeing is the dusty plane of our solar system illuminated by the Sun – a reminder that Earth is moving through a much larger cosmic structure.
So if you notice a strange triangle of light in the sky this winter, don’t dismiss it as leftover twilight. You might just be looking at one of the solar system’s most beautiful, and least talked-about, displays.
