What is a ‘Blood Moon’?

A Total Lunar Eclipse is often orange or copper, but rarely red

Read any newspaper or website in the run-up to a Full Moon and they’ll use the phrase ‘super Moon’ – an almost meaningless term – and it’s the same with a Total Lunar Eclipse.

‘Blood Moon’ is the preferred shorthand, but it’s not accurate; the Moon does not go red. Having observed a few, I’ve seen a totally eclipsed Moon turn a bright orange, a dull pink, and even a kind of copper-grey, but never red.

Why does it change color at all? The lunar eclipse can only happen at Full Moon, when our natural satellite is at its dazzling brightest. The Earth prevents the Sun’s light from directly hitting the Moon, but some sunlight does reach it by traveling through the Earth’s atmosphere. It’s same physics that causes the reddening of a rising and setting Sun.

However, the colors you can see during Totality vary enormously. It all depends on what’s going on in the Earth’s atmosphere. Volcanic eruptions that have thrown up ash in recent days and weeks can hugely affect what color the Moon turns. If there is ash in the atmosphere, it can go even an even deeper shade of pink or orange than normal.

There’s no way of knowing in advance what color the Moon will be during Totality, which is what makes a Total Lunar Eclipse so enthralling for Moon-watchers.

Photo credit: NASA