The Moon can be like a painter’s canvas, dabbed with many colors: the silver of a frosty night, the gold of honey, the orange of a ripe cantaloupe, even the deep red of blood. But it’s almost never blue – at least not in appearance. It sometimes is blue in name, though – including tonight. That’s because it’s the second full Moon of May – a repeat appearance known as a Blue Moon.

The color of the Moon – full or not – depends on several factors. When the Moon is low in the sky, as it rises or sets, its light passes through a thicker layer of air. Molecules in the atmosphere scatter blue wavelengths of light, allowing the red to shine through.

As the Moon climbs higher, we see more of its true color – gray. But the Moon is so bright that it looks white or silver.

During a lunar eclipse, the Moon passes through Earth’s dark shadow. But sunlight filtering through Earth’s atmosphere makes the Moon look dark orange or red.

In rare cases, the Moon can actually look blue. That happens after volcanic eruptions or big forest fires. These events pump out particles that scatter red light, allowing the blue to shine through. After the eruption of Krakatoa, in 1883, the Moon appeared blue for months around the entire globe.

Whatever its color, enjoy tonight’s Blue Moon. And look quite close to it throughout the night for the star Antares, the heart of the scorpion. They’ll be closest as they set.

Script by Damond Benningfield