The full moon appears a little bigger in the sky this weekend, but not all that much bigger or more dramatic than the average full moon.
This weekend's full moon will be physically closer to the Earth, about 221,000 miles away. That will make it 7 percent larger than an average full moon and about 14 percent percent brighter.
The reason it's a super moon is that it's in the right place at the right time. The moon's orbit around Earth is not quite a perfect circle. It's a slightly oval ellipse.
Because of that shape the moon's distance from us varies more than 30,000 miles as it orbits Earth every month.
Its farthest distance, called apogee, can be as far as 252,000 miles. Its closest approach is called perigee and can be as close as 220,000 miles.
So the full moon this weekend will occur when it's nearly at perigee, making the lunar orb appear slightly larger.
When a full moon occurs when the moon is at apogee it appears slightly smaller than average. Some call that a "wimpy moon."
The next wimpy moon will occur Jan. 15.
You can see the relative difference in size in the photo where a super moon has been superimposed on the photo of a wimpy moon.
Make sure to watch the big orange moon when it's rising in the southeast around sunset tonight.
The full moon always seems much larger when it's rising than it does when it's higher in the sky and that optical illusion will be even more extreme tonight.
You'll notice that the super moon o is taking a low track across the southern sky.
That happens with any full moon around the summer solstice, or first day of astronomical summer, which occurred Friday.
This time of year the full moon takes pretty much the same low path that the sun does around the winter solstice, the first day of winter.
This makes sense when you think about it because the full moon is always on the opposite end of the sky from the sun, so this time of year as the sun takes its high arc across the summer sky the full moon is a low rider.
Around the winter solstice in late December there's a flip-flop. The sun takes its low trajectory in the southern sky and the full moon around Christmas takes a high arc.
Physically the full moon always makes the ocean tides a little higher and the closer super moon may add a tiny bit to that.
Mike Lynch is author of "Stars, a Month by Month Tour of the Constellations."
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