This summer’s first supermoon will appear in the night sky on Saturday and is only the first in a lunar triple-play this summer. During Saturday night’s display, the July full moon will appear about 30 percent brighter and 14 percent closer than a normal full moon.
Last year’s June full moon made headlines with its super luminosity. This year, skywatchers will see three supermoons, one each during the back-to-back full moons in July, August, and September, according to Space.com.
Supermoons happen when the moon is closest to Earth at a point called “perigee” during its month-long orbit. The distance between the Earth and the sun is typically about 238,855 miles. At perigee, the moon is about 31,000 miles closer to Earth than at its farthest orbit, called “apogee.”
While it may seem rare that three supermoons are taking place in three consecutive months, Geoff Chester with the U.S. Naval Observatory explained that it isn’t that unusual. He stated, “Generally speaking, full moons occur near perigee every 13 months and 18 days, so it’s not all that unusual.”
To the untrained eye, a supermoon may not be easy to detect, thanks to clouds and no point of reference for what the celestial body normally looks like. However, this year’s perigee moons will also have a “moon illusion,” allowing them to appear noticeably larger.
The moon illusion happens when the moon rises and stays near the horizon. Astronomers don’t fully understand why, but low-hanging moons appear much larger when they are seen through other objects in the foreground. Chester explained, “The moon illusion is probably what will make people remember this coming set of full moons, more than the actual view of the moon itself.”
The Chicago Tribune notes that Chester and other astronomers aren’t thrilled with the term supermoon. They worry that the phrase hypes up a rather common phenomenon and lead to public misinformation.
Chester explained to NASA’s ScienceCast, “I guarantee that some folks will think it’s the biggest moon they’ve ever seen if they catch it rising over a distant horizon, because the media will have told them to pay attention to this particular one.”
He added that there were three of the moons last summer as well, but only one was hyped up. Despite the common phenomenon, this weekend’s full moon will still put on a great display. As long as the weather is clear, everyone should be able to see the larger moon on Saturday night. The other supermoons will happen on August 10 and September 9.
[Image by Crusier]