Several years ago, a supermoon was scheduled to rise on a chilly evening in metro Detroit. My daughter was excited about seeing it, so we drove to her future high school, climbed to the top of the bleachers with a clear view looking east and waited for moonrise.
But a layer of low clouds moved in so we only saw the moon briefly before it "rose" to where it went behind the clouds. Still, during those fleeting minutes, she stared at the moon more closely than she ever had and saw craters with her naked eye as we sat together in silence, before she pronounced it "the coolest thing I've seen."
The only supermoon of 2017 happens this weekend. A supermoon has been defined since 1979 (when astrologer Richard Nolle coined the term) as a full moon which occurs with the moon at or near (within 90% of) its closet approach to earth in a given orbit.
When the moon rises around here this Sunday during the twilight at 5:32 pm, it will look bigger and brighter than a typical full moon. The weather looks like it will cooperate nicely for viewing. The temperature should be in the low 40s with only patchy clouds expected and nothing more than a gentle breeze.
This weekend's moon will be about 225,000 miles away, compared to an average distance of 238,000 miles from Earth. The moon also looks bigger just as it rises and sets because at those moments, we're viewing it at such a low angle that our line of vision passes through more of the atmosphere, which acts something like a magnifying glass. That's a big part of the reason that the moon doesn't look nearly as big once it gets high overhead, supermoon or not.
A supermoon can look up to 14% bigger and up to 30% brighter than a normal full moon. But any full moon is worth a good long look, and Sunday evening's weather will be more pleasant for being outside than is typical for December in the Detroit area.
Some people claim that the difference is tough to notice, and that this is mostly hype. But that evening with my daughter was memorable. It was super. And it involved the moon. That's my definition of a supermoon.
