A supermoon rises over West Yorkshire in the U.K. last year. // Photograph from Back Page Images/Rex Features/AP

Andrew Fazekas
for National Geographic News
Published May 3, 2012

On Saturday night, the full moon will be closer to Earth than at any other time this year, an occurrence that’s been labeled a supermoon.

Due to the moon’s egg-shaped orbit, there are times when our natural satellite is at perigee—its closest to Earth—and at apogee, its farthest.

The term “supermoon” was coined in 1979 to describe a full moon that coincides with perigee—something that happens about once a year, on average.

During this week’s perigee, the moon will be 221,801 miles (356,955 kilometers) from our planet, and that close approach will happen within minutes of the official full moon phase, which occurs at 11:35 p.m. ET.

“As a consequence, this translates into it appearing as much as 16 percent bigger and 30 percent brighter than other full moons of 2012—not a huge amount, but definitely noticeable,” said Geza Gyuk, an astronomer at the Adler Planetarium in Chicago.

The moon’s proximity won’t have any major effects on our planet, according to astronomers, who hope to dispel fears that the looming lunar orb causes natural disasters.

“While we know that during new and full moons the tides are greatest—and if it’s in concert with a storm surge it might produce unusual flooding—there is no scientific evidence that earthquakes and other natural disasters are connected,” Gyuk said.

“Supermoons have been happening for billions of years, and nothing particularly special occurs on these dates—except, of course, for a beautiful full moon.”

Another Supermoon on the Horizon

For photo hounds, the most picturesque moments during Saturday’s supermoon will occur in the minutes after local sunset, as the full moon hovers above the horizon.

“What you should see is the moon rising, deeply colored and looming over the foreground objects,” Gyuk said. (Related pictures: See how a lunar eclipse turns the full moon red.)

Because the size of the moon’s orbit varies slightly, each monthly perigee is not always the same distance from Earth.

In March 2011, for example, sky-watchers were treated to the closest supermoon in two decades, when the moon was a mere 221,565 miles (356,575 kilometers) from Earth.

And next month the full moon will again roughly coincide with perigee, albeit one that puts the moon a bit farther away, at 222,750 miles (358,482 kilometers), Gyuk said.

“The full moon will appear to be just half of one percent different in size,” Gyuk said. “So if you miss this month’s supermoon, don’t worry, you can see it again when it is only one percent less bright.”

Photograph by Babak A. Tafreshi, TWAN

Light seems to pool at the bottom of the full moon in a picture of a lunar eclipse taken from Iran in 2008.

This weekend sky-watchers in western North America will be able to catch a similar sight during the last total lunar eclipse until 2014. The moon show will be visible from the Pacific coast on Saturday at dawn, appearing low in the western horizon.
The entire lunar eclipse will be visible from East Asia, Australia, and the far western part of North America, including Alaska as well as Canada’s Yukon and Northwest Territories.

The eclipse will last for three and a half hours, starting at 4:45 a.m. Pacific time.

Posted by Andrew Fazekas April 30, 2011 
Uranus photograph courtesy NASA

For night owls, Saturn will be the sole planet on display in the evening skies over the course of the next month. But early-birds will get a chance to see a “family reunion” of worlds above the eastern horizon at dawn.

The sky show kicks off this weekend as the waning crescent moon pays a visit to both Uranus and Venus.

For the first stop on Saturday, the moon will act as a convenient guidepost to tracking down the seventh planet in the solar system, the icy gas giant Uranus.

Look for the planet about six degrees—or the equivalent of 12 full-moon disks—to the right of the moon.

Normally Uranus is quite a challenge to track down for beginner sky-watchers because of its faintness. After all, the planet lies about 1.8 billion miles (3 billion kilometers) away from the sun.

Shining at a magnitude of 5.5, which is just barely visible to the naked eye from a dark countryside, Uranus is more easily hunted down from the suburbs using binoculars or a small telescope. These optical aids reveal it as a tiny greenish disk set against the inky blackness of space.

By Sunday at dawn, the moon will seem to have have snuggled up to the goddess of love, Venus.

The cosmic pair will be separated by about 8 degrees—16 full-moon disks. Unlike Uranus, the much closer Venus—only about 124 million miles (200 million kilometers) away—is the brightest star-like object in the heavens now.

What’s more, Venus won’t be alone, although finding its companions will present more of an observing challenge the next few nights.

—Image courtesy Starry Night Software

With binoculars you’ll be able to spot tiny Mercury just to the lower left of brilliant Venus.

Even closer to the horizon, below the moon, will be Jupiter next to a fainter, ruby colored Mars.

Unfortunately these planets will be close to the horizon and will be quickly drowned out by the glare of the rising sun.

But don’t fret though if you can’t locate all the planets now, because this cosmic parade is just a preview for a really beautiful gathering of worlds peaking in a couple of weeks, when the planets all climb much higher in the morning sky. So stay tuned!

(I apologize in advance that this already passed, but did anyone else notice how amazing the moon was last Saturday?)

Andrew Fazekas
for National Geographic News
Published March 17, 2011

It may not be faster than a speeding bullet, but Saturday the moon will make its closest approach to Earth in 18 years—making the so-called supermoon the biggest full moon in years.

And despite Internet rumors, the impending phenomenon had no influence on the March 11 Japan earthquake and tsunami (see pictures).

The monthly full moon always looks like a big disk, but because its orbit is egg-shaped, there are times when the moon is at perigee—its shortest distance from Earth in the roughly monthlong lunar cycle—or at apogee, its farthest distance from Earth.

Likewise, because the size of the moon’s orbit varies slightly, each perigee is not always the same distance away from Earth. Saturday’s supermoon will be just 221,566 miles (356,577 kilometers) away from Earth. The last time the full moon approached so close to Earth was in 1993, according to NASA.

The March 19 supermoon, as it’s called, will be visible “pretty much any time during the night,” said Geza Gyuk, astronomer at the Adler Planetarium in Chicago.

“Look for the full moon as it rises above the eastern horizon as the sun sets below the western horizon—it will be a beautiful and inspiring sight,” he said via email.

Though the supermoon will be about 20 percent brighter and 15 percent bigger than a regular full moon, the visual effect may be subtle, added Anthony Cook, astronomical observer for the Griffith Observatory in Los Angeles.

“I doubt that most people will notice anything unusual about this full moon,” Cook said.

“Because the total amount of light is a little greater, the biggest effect will be on the illumination of the ground—but not enough to be very noticeable to the casual observer.”

Japan Earthquake Not Linked to Supermoon

Such a lunar close encounter can cause slightly higher than normal ocean tides and localized flooding—especially if there is already a storm surge, astronomers say.

A supermoon may even have some impact on seismic activity because of the stronger gravitational interaction between the moon, the sun, and Earth.

Even so, there is no clear evidence that any of these phenomena influenced the Japan earthquake and tsunami.

“The earthquake in Japan happened when the moon was close to its average distance to Earth—there was nothing extreme about its position or phase,” Cook said.

“While some earthquakes seem to have tidal connections, this isn’t one of them.”

There’s no need to get worked up over a supermoon, Adler Planetarium’s Gyuk added.

“We survived 2008 [an almost supermoon year] and 1993 just fine,” he said by email.

“Just keep in mind even this ‘extreme’ supermoon is not really that extreme!”