You may have heard about the “supermoon eclipse” that will happen this Sunday, September 27. Sounds pretty exciting! But what does it mean? Let’s start with the “supermoon” part. The Moon’s orbit around the Earth is not a perfect circle; it’s an ellipse, which means that the distance between the Moon and the Earth changes over the course of a month. When the Moon is in the part of its orbit that brings it closest to Earth, the perigee, it appears larger in our sky. A full Moon that occurs during perigee is known as a “supermoon” in popular culture because it looks bigger. But don’t worry, you won’t need your sunglasses at midnight. A supermoon appears only 14% wider and 30% brighter than a “micromoon,” when the Moon is at apogee, the farthest point in its orbit. The difference between perigee and apogee is just 48,280 kilometers (30,000 miles), which sounds like a lot until you realize that’s a mere 12% of the average distance from Moon to Earth.

This image consists of two photos taken by Stefano Sciarpetti, with a micromoon shown in front of a supermoon.


Enough with the numbers, let’s see how it looks! Here’s a visual comparison that was featured as NASA’s Astronomy Picture of the Day in 2014. This image consists of two photos taken by Stefano Sciarpetti, with a micromoon shown in front of a supermoon. See the size difference? It’s not much, and it’s really hard to notice when you’re standing outside looking at a Moon suspended in an ink black sky.

But still, it’s fun to know that we will have a supermoon during this weekend’s total lunar eclipse! This one is the last in a series of four eclipses that have been spaced six months apart over the past two years. After this Sunday, there won’t be another total lunar eclipse until 2018!  And unlike some recent eclipses that happened at ridiculous hours of the night, this one is nicely timed in the evening from about 9:00 pm to 12:30 am EDT, with totality (when the Moon is entirely within the Earth’s shadow) from 10:11 pm to 11:23 pm EDT. The supermoon eclipse will be visible from most of North and South America, Europe, and Africa. For any young children in your life, our Science in Pre-K educators wrote up this great conversation about the eclipse.

If you’ll be near the Museum that night, stop by our Phoebe Waterman Haas Public Observatory to view the eclipse with us! We will be open from 8:00 pm to midnight, weather permitting, with our telescopes pointed at the Moon and other fun astronomical sights. Check the Observatory’s Twitter feed the day of the event for closure notices and weather updates.

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