Moon Gazers to Get Quadruple Treat Tuesday Night

Tonight’s combination of lunar events might sound like a fancy gymnastics move or the feature dish at a swanky five-star restaurant. All the adjectives piled on this evening’s partially eclipsed harvest blood supermoon have their purpose, though. They help astronomers, stargazers, and farmers figure out what they’re looking at. 

Assuming your night isn’t cloudy and you live in North or South America, a peek at the sky sometime after 10:44pm Eastern should reveal the moon in fine form. It’ll seem bigger than average (a supermoon). It’ll have a reddish tint (a “blood” moon). The top part will seem cut off (partially eclipsed). Oh, and it’ll be the last full moon you can see before summer turns to fall on September 22 (the “harvest” moon).

The science behind tonight’s sky-show has to do with Earth’s position in relation to the moon and sun. When Earth casts its shadow, also known as its umbra, on the moon, it blocks the sun’s rays. This darkens the moon’s face. A complete blockage of light results in an eclipse. If some light does manage to get past but is still filtered by Earth’s closeness (a “penumbra”), it can cast a dimmer, reddish shadow. When the moon looks rusty like that, it’s called a “blood moon”.

As for the moon’s super status? That results each time the moon is at the closest point of its wavy orbit around Earth. This closest point is called “perigee.” It can make the moon appear larger and brighter when gazed at from below. Full supermoons aren’t all that rare. We’ll see another on October 17. But the next partially eclipsed harvest blood supermoon? We’ll have to wait until 2033 for that one, astronomers say.

Reflect: What do you think is most fascinating about watching the night sky?