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The ‘Supermoon’

Anxious journalists and amateur scientists have spent the past several weeks fretting over the larger-than-usual moon set to appear in our night sky this Saturday, March 19. On that night, the moon will be fully illuminated at the same time as it reaches its lunar perigee, the closest point in its elliptical orbit around the Earth.

Astrologer Richard Nolle has branded the event an “extreme Supermoon” and spurred fears that the moon’s proximity could cause natural disasters here on Earth. He did so before last week’s devastating earthquake and tsunami in Japan. But when Need to Know called the National Optical Astronomy Observatory (NOAO) for more information, officials there told us there was nothing to worry about and there is no connection between this gigantic moon and natural disasters. “This is not something that astronomers are paying attention to,” said NOAO astronomer and public information officer Dr. Stephen Pompea.

So what’s really happening on March 19? Here are five things you need to know about the Supermoon, compiled with Pompea’s help.

1. Supermoons happen all the time.

The moon has an elliptical orbit, which means that it is closer to Earth during some parts of the month than others. During the lunar apogee, the point at which the moon is farthest from Earth, there are about 252,711 miles (406,700 km) between the centers of the two celestial bodies. During the lunar perigee, which occurs every month, the moon is more than 30,000 miles (50,300 km) closer. The term “Supermoon” refers to a full moon that occurs near that perigee. “Although it sounds extraordinary,” said Pompea, “it is not, and it happens frequently.”

An “extreme Supermoon” is a new or full moon that occurs at the exact lunar perigee. According to Nolle’s website, Earth experienced extreme Supermoons in 2010, 2008, and 2005.

2. Don’t expect the world to end.

Yes, the 19-year lunar Metonic cycle, in which the phases of the moon land on roughly the same calendar days as they did in the previous 19-year cycle, might mean that the lunar perigee will be slightly closer on March 19 than it has been since 1992, and tides might rise a little bit in response. “When the moon is closer, tides are bigger,” said Pompea. But don’t expect anything catastrophic. The moon is only about a thousand miles closer to the Earth than it was during last month’s lunar perigee. “We had a big, big tide last month, and we’re going to have one next month. This isn’t an isolated event, it’s something that’s pretty similar to last month and will be pretty similar to next month.” Pompea conceded that marginally higher tides could mean trouble in some coastal areas but said that the likelihood of global problems resulting from the perigee is very low.

3. Past “extreme Supermoons” have had less-than-dramatic results.

Some commentators have tried to connect the dates of past extreme Supermoons to environmental disasters, pointing to events like the 2004 Indian Ocean tsunami, which occurred 15 days before the January 10 extreme Supermoon, and Hurricane Katrina, which occurred more than seven months after, as proof of the moon’s power. The recent earthquake and tsunami in Japan has no doubt added fuel to these theories. But this argument, which attributes a year’s worth of disaster to one night’s lunar activity, has not helped Nolle’s case. The facts don’t point to any correspondence between the lunar perigee and those events, Pompea said, adding that people who are convinced that the Supermoon triggers natural disasters need to “show us. You need to tell us, ‘the Supermoon was on that date and this happened.’”

“If you try hard enough you can chronologically associate almost any natural disaster/event to anything in the night sky,” astronomer David Reneke told, dismissing the theories.

4. Don’t call it a Supermoon when you’re talking to a professional.

Forget that dramatic title, said Pompea. “No astronomer would recognize the term ‘Supermoon.’ It’s not something we’ve ever heard of and it’s not something we’d use.”  Nolle, the man who invented the term, is a “certified professional astrologer” whose website boasts that he predicted the 1993 World Trade Center bombings, the recent recession and Hurricane Katrina, among many other major events, using astrology. Nolle first used the world “Supermoon” in a 1979 article in Horoscope Magazine.

5. Expect a bright, beautiful full moon that looks a lot like all the others this year.

The moon will definitely be closer on March 19 than it has been in a long time, but we may not be able to tell. Pompea says that the moon will probably not be obviously larger or brighter on that night, though the difference between this moon and its predecessors would probably be evident in a comparison of two photographs. Other experts, like NASA astronomer Dave Williams, are slightly more optimistic. “Because it’s a full moon at its closest approach,” he told ABC News, “it’s going to be big and really bright.” Williams recommended that you take the time to see it. “This is the biggest full moon that you will ever see,” he said. “You will see the moon again, but this is as big as it gets.”