Rare Supermoon Rises This Weekend: Slideshow of Beautiful Past Supermoons

Be sure to look up into the sky this weekend, because a once-a-year phenomenon dubbed the "Supermoon" will be lighting up the sky as the Sun goes down this Saturday night into Sunday morning. And judging from the 15 images we have of previous years' Supermoons, it's an event you won't want to miss.

The "Supermoon" is actually a once-a-year coincidence of two events: the Moon is at its fullest-lit phase of the month while another monthly astronomical event occurs at the same time, when the Moon arrives at what's called its "perigee." That means it is at its closest point to the Earth, only 221,824 miles away, compared to 252,581 miles away at its most distant.

The Moon reaches perigee about once each month. Earth also gets to see a full Moon about once a month. But in this case, according to NASA, the perigee of the Moon, at exactly 7:32 am Eastern Daylight Time (4:32 am Pacific) on Sunday June 23, and when the Moon becomes officially full are only hours apart.

The result? A huge, brightly lit, beautiful Moon in the sky. According to NASA, this year's Supermoon will be up to 14 percent larger and 30 percent brighter than a typical full Moon. The Moon won't be closer to Earth than it is on Sunday for more than a year - August 2014.

If you can't make it outside on Sunday night (or it's unfortunately cloudy) in order to see the official Supermoon, don't worry - do it on Saturday or Monday. The Moon will still be noticeably larger and brighter than usual on those days, and you're sure to get a great show. Also, if you can catch the Moonrise at about 6:30 pm (if the Sun's not too bright) or the Moon set at about 3:30 am, you'll get the chance to see the Moon look absolutely enormous. Called the "Moon illusion," the Moon appears much larger near the horizon than it does in the sky.

If your location is very unfortunately cloudy all weekend, you can still see the phenomenon online, through SPACE.com's web stream of the event.

Of course, you also shouldn't worry about this astronomical event. The Moon will look 14 percent larger, but it's actually only a few percent closer to the Earth than usual, and perigee is a common occurrence - it's just when it coincides with a full Moon that's rare. There will be a larger range of high and low ocean tides, as a result of the Supermoon, but tides will lag behind the Moon's perigee by a couple days, according to CBS News. High tides will reach cities between about 12 hours and two days after the Moon's official perigee.

So don't be afraid, go outside, and enjoy this rare event. And check out our slideshow for amazing images from previous "Supermoon" events.