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SALT LAKE CITY — The biggest full moon of the year is set to rise Saturday night, coinciding with the eta Aquarid meteor shower and threatening to outshine the annual shower.
A supermoon — what scientists call a perigee full moon — occurs when a full moon coincides with it reaching the closest point to Earth in the moon's elliptical orbit.
The moon will come within 221,802 miles of Earth on Saturday night; technically at its closest at 9:34 p.m. MDT.
Just one minute later, the lunar orb officially becomes full, but the best time to view the moon will be a bit earlier, right around sunset, just after the moon crosses over the horizon. The moon will appear 14- to 16-percent larger and 30-percent brighter, according to NASA, and the effect will be amplified before the moon fully rises.
"For reasons not fully understood by astronomers or psychologists, low- hanging moons look unnaturally large when they beam through trees, buildings and other foreground objects," NASA wrote. "On May 5, this 'moon illusion' will amplify a full moon that's extra-big to begin with."
The eta Aquarid meteor shower, made up of the remains of Halley's comet, also hits its peak Saturday night, although it may be difficult to see because of the supermoon.
"Its light will wash out the fainter eta Aquarid meteors," NASA meteor expert Bill Cooke of the Marshall Space Flight Center told Space.com in an email. Cooke said the brightest parts of the display may still be visible, though.
"Our fireball cameras have already detected four bright ones. So I would say that the odds are pretty good that folks can see a bit of Halley's Comet over the next few days, if they care to take the time to look," he said. "They will be the big and bright ones, fewer in number with a rate of just a few per hour, but they will be there."
The meteor shower is expected to peak Saturday at up to 60 meteors per hour. It began April 19 and ends May 28.
The last supermoon occurred March 19, 2011, and brought the moon a bit closer to Earth; however, Saturday's supermoon will appear to be larger due to the one-minute difference. In 2011, there was a 50-minute wait between the moon reaching perigee and becoming full.
Scientists have tried to dispel fears that supermoons cause chaos on Earth, as full moons are often superstitiously believed to raise disaster and crime rates and even cause people to behave in strange ways — the term "lunatic" derives from the Latin "lunaticus," meaning "of the moon" or "moonstruck."
During supermoons, Earth sees a less than 1-percent increase in seismic activity, and only a slightly larger increase in volcanic activity.
