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[[{"type":"media","view_mode":"media_large","fid":"39360","attributes":{"class":"media-image","typeof":"foaf:Image","style":"","alt":"Why is a supermoon super?"}}]]Tonight – at 9:38 PM EDT – if you walk outside and look into the sky, you’ll see a big, beautiful full moon. But it won’t be just any full moon; it will be a supermoon!
Why will tonight’s moon be super? We answer this question with help from Universe Today and Slate.
Every 27 days, the Moon completely orbits Earth. When the Moon positions itself opposite the Sun, the half that faces us lights up. We call this a full moon.
Slate explains that “because the Moon orbits the Earth in an ellipse, not a circle, the distance between us and the Moon changes all the time.”
When the Moon is closest to Earth in orbit, it reaches perigee. Conversely, when the Moon is farthest from Earth in orbit, it reaches apogee.
For a supermoon to occur, the Moon must reach its perigee within 24 hours of becoming a full moon. If this happens, the already big and bright full moon appears a little bigger and a little brighter.
Twenty-two hours and eight minutes before tonight’s moon becomes full, it will reach its perigee at about 222,691 miles from Earth. Because it will reach this distance within 24 hours of becoming full, the moon will be considered a supermoon.
While this moon might be super, it’s not quite as super as the full moon that occurred on June 23, 2014. That night the Moon perigee happened just 27 minutes before the moon became full!
Looking for more Never Stop Asking "Why?" questions? Catch up on all of the past "Whys" on the blog!
