Sunsets in northern Australia have recently displayed unusual color patterns due to crepuscular rays, an optical illusion. This phenomenon, observed in the Top End in May 2025, creates distinct ribbons of blue sky amid typical sunset hues.
What Are Crepuscular Rays?
Crepuscular rays occur when the sun is partially obscured by low-hanging clouds, casting visible beams of sunlight. The Bureau of Meteorology (BOM) meteorologist Hanna Whiteside explained that the beams are actually shadows from clouds.
The name comes from Latin for twilight, the time they are most visible from land. They are also known as God's rays or Jacob's ladder. The phenomenon can occur any time the sun is visible, but is most photographed at sunset because scattered light creates vibrant colors.
How Do They Happen?
According to Whiteside, crepuscular rays occur when there is low cloud and enough particulate matter to scatter light. When the sun sets behind a cloud near the horizon, shadows radiate in beams.
The appearance depends on cloud shape and atmospheric particles.
Recent preventive burns in the Top End have increased smoke in the air, raising the chance of conditions favorable for crepuscular rays.
Perspective and Counterpart Phenomenon
Crepuscular rays appear to radiate outward from the sun due to perspective, but the beams are actually parallel. An inverse effect, anti-crepuscular rays, can appear on the opposite horizon.
Occurrence and Frequency
Crepuscular rays can happen at any time of day, but at sunset the thicker atmosphere creates scattered red and orange colors. The BOM noted that many recent Darwin sunsets have featured crepuscular rays.
The phenomenon can occur anywhere in the world and at any time of year.