A supermoon will occur this weekend, peaking the night of Saturday, June 23. It will also be the Summer Solstice, marking the beginning of summer. The Summer Solstice is the longest day of the year.

The 2013 supermoon will be the largest supermoon this year.

The supermoon, also known as a perigee full moon, will light up the Summer Solstice sky, enchanting backyard astronomers everywhere.

The supermoon will appear up to 14 percent bigger and 30 percent brighter than a normal moon.

The moon's distance to Earth varies constantly, tracing an ellipsis around the planet as it travels. A supermoon occurs when a full moon is nearest to Earth.

The moon lines up with Earth and the sun at a specific point called the lunar perigee, and a super-bright supermoon lights up the night sky. Astrologer Richard Nolle coined the term.

The supermoon will also affect the tides. "The body of the Earth is fairly rigid, so it does not stretch much, but the oceans are much more easily moved," astronomer Larry Sessions wrote. "Thus the effect piles up water on either side of Earth, and these piles of water - created by the differential gravitational effect - are the tides. Note that, on average, the tidal effect is quite small. It raises tides only a few feet across an 8,000-mile-wide planet Earth."

This effect is always occurring, but the Supermoon will boost it. On the longest day of the year, as the Summer Solstice occurs, the Supermoon will light up the sky.

There will be another Supermoon in July, but it will not be as bright. This weekend's Supermoon will mark the closest the full moon will be to Earth until August 2014.

At 7:32 AM EDT Sunday, the moon will be exactly full. It will reach the closest point to the Earth 22 minutes before that. On both Saturday and Sunday evening, the moon will be particularly bright. It is easiest to see when it is closest to the horizon at moonrise or moonset.