What Is Zodiacal Light – See False Dusk or False Dawn
The zodiacal light is one of the most magical and subtle sights in the night sky — a cone of light stretching from the horizon. You can easily locate it in your sky using the astronomy app Sky Tonight. Often called the “false dawn” or “false dusk,” it actually has nothing to do with the Earth's atmosphere. Curious to find out what it really is? Let's dive in.
Contents
- What is zodiacal light?
- When to see zodiacal light?
- How can I see zodiacal light?
- F.A.Q.
- Zodiacal light: bottom line
What is zodiacal light?
The zodiacal light is a hazy pyramid of light located above the sunrise or sunset point on the horizon. It’s centered on the ecliptic – the Sun’s path in the sky that crosses the well-known zodiac constellations. This is why it's called the zodiacal light.
You might have noticed the zodiacal light, not even realizing what it is. It looks like the light of the nearby town or the lingering twilight. You might also confuse the zodiacal light with the Milky Way, and that's not surprising. It is comparably bright and even milkier in appearance, but you can tell the zodiacal light by its pyramidal shape. Under a dark sky, you can sometimes even see the real Milky Way crossing with the zodiacal light.
What causes zodiacal light?
You can distinguish the zodiacal light from the real twilight by the fact that it has no reddish tinting – the pink color is the effect of the Earth's atmosphere, but the zodiacal light comes from outside our atmosphere. In fact, it’s just the Sun's light reflecting off dust grains orbiting our star in the inner Solar System. But where do these dust grains come from? Scientists have long assumed that the space dust that causes the zodiacal light is produced by asteroids and comets. However, the new research shows that the main source of this cosmic dust may be dust storms on Mars.
Is zodiacal light false dawn or false dusk?
The zodiacal light is both false dawn and false dusk, only at different times of the year. In spring, in both hemispheres, the zodiacal light occurs right after the real dusk, so it’s called “the false dusk.” In autumn, the zodiacal light occurs just before the real dawn and is known as “the false dawn.” Note that the seasons in the Northern and Southern hemispheres are reversed.
When to see zodiacal light?
In both hemispheres, at mid-latitudes, the zodiacal light is best seen around the equinoxes. In tropical latitudes, it can be seen year-round.
Spring zodiacal light – false dusk
In spring, the zodiacal light can be seen for about an hour in the western sky. Start observing the “false dusk” about 90 minutes after sunset.
In the Northern Hemisphere, it appears in the sky in late February, reaches its maximum brightness around the March equinox, and lasts until early May.
In the Southern Hemisphere, the zodiacal light appears in the sky in late August, reaches its maximum brightness around the September equinox, and remains until early November.
Autumn zodiacal light – false dawn
In autumn, the zodiacal light can be seen for about an hour in the eastern sky. Start observing the “false dawn” about 90 minutes before sunrise.
In the Northern Hemisphere, it appears in the sky in late August, reaches its maximum brightness around the September equinox, and remains until early November.
In the Southern Hemisphere, the zodiacal light appears in the sky in late February, reaches its maximum brightness around the March equinox, and lasts until early May.
How can I see zodiacal light?
First, find a location with a dark sky, away from city lights, as the zodiacal light is faint and easily washed out by any bright source, including the Moon. The darker the sky, the better your chances of seeing the zodiacal light. Check your sky’s darkness level on the Bortle Scale with our handy infographic.
The best time to see the zodiacal light is around the equinoxes. The next one is on March 20, 2025, but it coincides with the waning gibbous Moon, which will overshadow the false dawn/dusk. Luckily, you’ll have a few months around this date to catch the zodiacal light. For the best view, choose a moonless night close to the equinox, such as March 29, 2025, when the Moon will be in its new phase.
How to find zodiacal light in the sky?
The stargazing app Sky Tonight will help you spot the zodiacal light. First, find out the time of the zodiacal light in your location:
- In the Time Machine section at the top of the main screen, select the date you want to observe the zodiacal light. The next best time to observe it is on March 29, 2025, the date of the New Moon closest to the March equinox.
- Look up the sunrise and sunset time on that date. To do this, find the Sun on the main screen (or with the app’s search), tap on it, go to the Events section, and check the Visible Passes.
- In the Northern Hemisphere, subtract 90 minutes from sunrise time – it’s when you should start looking for the zodiacal light.
- In the Southern Hemisphere, add 90 minutes to sunset time – it’s when you should start looking for the zodiacal light.
- If you don't want to miss the moment, set a reminder.
On the chosen date and time, go to a place with dark, clear skies and find the zodiacal light’s direction. Depending on your hemisphere, it's located above the sunrise or sunset point, so you need to find this point:
- In the Northern Hemisphere, tap the blue sunrise time on the chosen date in the Sun’s Visible Passes section, and the app will show you the Sun’s location on the sky map.
- In the Southern Hemisphere, tap the blue sunset time on the chosen date in the Sun’s Visible Passes section, and the app will show you the Sun’s location on the sky map.
- Tap the blue compass button at the bottom right of the screen. The app will use your device’s location to adjust the image to match the real sky above you.
- Follow the white arrow on the screen to the sunrise or sunset point. This is the direction to see the zodiacal light extending from the horizon.
F.A.Q.
Is zodiacal light related to the zodiac signs?
The zodiacal light is an astronomical phenomenon, while zodiac signs are part of astrology. The only connection is that they both share the term "zodiac," which refers to the band of the sky where the zodiacal light and constellations are found. Discover more about the zodiacal constellations and how they differ from the zodiac signs in our separate article.
What is zodiacal dust?
Zodiacal dust is a dense disc of interplanetary dust particles located near the plane of the Solar System. It is formed in a pancake-shaped cloud and is a source of the zodiacal light.
What does a false dawn mean?
A false dawn is the zodiacal light in spring. Apart from stargazing, it is significant for practitioners of the Islamic faith. It plays a role in determining specific prayer and fasting times.
What is the difference between zodiacal light and gegenschein?
Gegenschein, like the zodiacal light, is caused by sunlight reflecting off interplanetary dust, but it appears directly opposite the Sun in the sky, centered at the antisolar point. Gegenschein forms a slightly brighter, oval-shaped spot about 8-10° across within the dimmer band of the zodiacal light. Gegenschein is even more difficult to detect than the zodiacal light, requiring a perfectly dark sky and the use of the averted vision.
Zodiacal light: bottom line
The zodiacal light is a rare and beautiful celestial phenomenon that looks like a hazy pyramid of light rising from the horizon. It occurs just after dusk near the vernal equinox and just before dawn near the autumnal equinox. The next best time to see the zodiacal light is from March to early May 2025. To make sure you see this mysterious light in all its glory, pick a moonless night, head to a dark suburban location, and use the free Sky Tonight app to guide your way.
Good luck on your stargazing journey!
