Look out for some changes in the sky on Sunday, when a supermoon will be visible.
“People can see it anywhere (as long as it’s not cloudy),” Dr. Noah Petro of NASA’s Goddard Space Flight Center told Fox News via email. “Unlike the solar eclipse, you don’t have to be in (sic) particular spot to see it. Just go out after dark and look up!”
Read on for a look at the science behind the phenomenon and what you should know about watching it.
What is a supermoon?
Astrologer Richard Nolle came up with the word. His definition, via EarthSky, is when there is “... a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit.”
It's “a very weird definition,” Dr. Jackie Faherty, a senior scientist in the department of astrophysics at the American Museum of Natural History, told Fox News.
She said that “there’s not really a good example of the superest of the supermoons.”
“Some of them will be much closer than others,” Faherty said.
Three new moons earlier this year -- in addition to Sunday’s full moon -- meet Nolle's criteria for supermoons, EarthSky reports.
“The definition we at Goddard use is the closest full Moon in a 14 month cycle, so once every 14 months,” Petro wrote. The Dec. 3rd full moon is considered a supermoon.
“If you use a looser definition of the full Moons when it’s within 90% of being closest (which appears to be the common definition) then there are multiple super moons in a year, which makes it much less rare,” he explained.
What's different about it?
“A supermoon compared to the average moon is 14 percent larger but 30 percent brighter,” Petro said.
However, he explained that “the normal observer will not notice the difference from full moon to full moon.” Petro suggested people regularly watch the moon during different phases and look out for changes.
“It is a closer full moon than what you’d be used to, but not one that you’d be paying particular attention to,” Faherty said.
How can I see the supermoon?
Faherty said to “just go outside and look at it.”
“If you watch a moonrise, it’s not related to a supermoon but can give you an effect that you want,” she explained. When the moon is on the horizon, there's an optical illusion where it seems bigger.
You'll need to have “a clear view to the horizon,” Faherty said. You can use the U.S. Naval Observatory website to search for moonrise times in your area.