Why Was the Moon Orange Last Night? Here's Why It Can Change Colour

Twitter has lit up with reports from around the U.S. and U.K. that the moon appeared orange or pink on Thursday night.

It is unclear exactly how widely the phenomenon was reported. Users reported the sight in various states across the U.S. including Louisiana, Illinois and Indiana.

One user based in New Orleans wrote in the early hours of Friday: "The moon was orange last night, sorry to whoever didn't get to see it."

Other tweets were posted the same morning, seen below.

Reports also came from various locations around the U.K. One Twitter user, based in Kingswood, South Gloucestershire, wrote: "My cat rudely woke me at 4am, but how glad am I! I slowly opened my eyes and maybe due to the 'just waking' vision, I saw the warmest, dusty pink moon outside."

It is not uncommon for the moon to appear red, orange, or pink. Sometimes, this is due to its angle in the sky. The nearer the moon is to the horizon, the more likely it is to appear orange.

This is because of the way light is scattered through the Earth's atmosphere. The atmosphere tends to allow certain colors of light, such as red, yellow, and green, to pass straight through. These colors are determined by the light's wavelength.

But some colors, such as blue, bounce off of particles in the atmosphere and separate from the rest. It's why the sky looks blue during the day.

When the moon is near the horizon, its light has to travel through more atmosphere to reach our eyes, compared to when it is directly above us. This causes blue light to scatter so much that more of the reds and yellows reach us. This is why the moon sometimes has an orange color.

Billy Teets, an astronomer at the Vanderbilt Dyer Observatory in Tennessee told Forbes in 2019: "As the moon gets higher in the sky, its coloration will fade to its normal greyish-white hue as you view it through less and less air."

While atmosphere thickness is one important factor, another is dust. Forest fires or ash from volcanic eruptions can also scatter sun or moonlight, causing a brightly-colored sky. Pollution can also deepen the moon's reddish color.

Next month, stargazers can expect to see what is known as a supermoon—when a full moon coincides with the moon being at its closest point to Earth in its orbit.

It will be the closest supermoon of the year, and will occur on May 26 at 7:14 a.m. EDT. It will appear full for around three days starting on the evening of Monday 24, according to retired NASA executive Gordon Johnston in his monthly sky-watching update.