There is more to a “supermoon” than meets the eye.
Science governs the appearance of the largest full moon of the year, and this weekend you can check out the amazing lunar sight for yourself.
On Sunday (June 23), the moon will be at its closest point to Earth — called perigee. This relatively close brush will happen as the moon enters its fullest phase, creating the cosmic coincidence known as the supermoon. At its fullest and closest, the moon will appear about 12 percent larger in the sky.
“It doesn’t matter where you are, the full moon you’re seeing will be the biggest for 2013,” Michelle Thaller, the assistant director of science at NASA’s Goddard Space Flight Center said. “… That 12 percent size different can mean as much as a 30 percent change in the brightness, so this will be a particularly bright supermoon.”
A changing distance
Supermoons occur about once annually, and this year, the supermoon is closer than it has been in a little while, Thaller said.
The distance from the Earth to the moon varies along the rocky satellite’s elliptical orbit. Perigee differs from month to month, so sometimes the supermoon is a little closer or further away, Thaller said.
“The closest the moon gets can actually vary much as much as the diameter of the Earth,” Thaller said. “That seems like a pretty big number, but the moon is actually 30 times the diameter of the Earth away from us. If you line up 30 Earths, that’s about the average distance of the moon away, but as it swings a little bit closer to us, that distance can vary.”
The sun can be to blame for the difference in distance. In the winter, when the Earth is closest to the sun, a supermoon could be even closer and more stunning, Thaller said. The strength of the sun’s gravity pulls both the moon and the Earth towards it slightly, making the moon dip closer to the planet.
Science from a supermoon
Although it might be a brilliant skywatching opportunity, not a lot of scientific research comes from the supermoon. Scientists prefer to study the moon from a closer vantage point, Thaller said.
“The supermoon for [scientists] is a fun chance to talk about the changes in the sky [and] observing the universe,” Thaller told SPACE.com. “As scientists, we like to observe the moon a little bit closer up and right now we have LRO, the Lunar Reconnaissance Orbiter, a spacecraft actually orbiting the moon. We’re taking these incredible high resolution pictures of the entire lunar surface.”
While some are calling it a supermoon, the astronomical community prefers to use the term “perigee full moon.”
And they’re not exactly rare, since the alignment between the full moon phase with perigee occurs every year, said Adler Planetarium astronomer Mark Hammergen.
But next year’s show on August 10, 2014, might be more specular than this one. That’s because it’s expected to be even closer—clocking in at just 356,896 kilometers from Earth, said Hammergren.
As for a supermoon coinciding with the solstice, that’s more unusual.
“This kind of celestial geometry repeats roughly every 14 years,” said Hammergren.
And if you thought a supermoon might bring out “super-effects” on Earth, think again. There is no scientific evidence for any connection between a supermoon and natural disasters.
It is, however, well known that tides are highest during new and full moons — which means if there is a storm surge during a new or full moon, then unusually high coastal flooding may occur.
“When the full or new moon occurs near perigee, there is a slightly stronger effect on the tides,” said Hammergren. “There have been coastal floods associated with storms hitting near spring tide at the time of perigee.”
Experiences of watching Supermoon
On Sunday, our lunar neighbor made its closest approach to Earth for the 2013 calendar year, appearing 8 percent larger and 17 percent brighter than usual.
At its closest, the full moon clocked in at a distance of 221,824 miles (356,991 kilometers) from Earth. That’s a bit closer than the typical distance of 226,179 miles (364,000 kilometers).
But what a difference it made.
“We saw it from the field with fireflies and hay bales. It bleached out the stars,” tweeted one poetic fan.
Others used the supermoon as a way to reflect.
“My cat is sad because yesterday’s supermoon caused him to contemplate our galaxy’s vastness & his smallness within it,” tweeted @MySadCat.
Some also marked the occasion by taking photos of the moon in spots all over the world.
PHOTOS: Each year Supermoon occurs, last year also it occured
See more photos here: