On June 23 2013 the Moon will be closer to the Earth than at any other point in all of 2013. This Supermoon — as it’s known — will appear about 14% larger and 30% brighter than a typical Full Moon does. The Moon will be at its closest distance to the Earth at exactly 7:32 am EDT (4:32 am PDT) on June 23 2013 — as a result of that timing, both the night of June 22 and the night of June 23 will offer good shows.
Something to note — this Supermoon will actually be the closest that the Moon will get to the Earth until August 2014, so enjoy the sight while you can.
The Supermoon is a regularly recurring event, it’s the result of the Moon reaching its perigree — the portion of its orbit where it’s closer to the Earth than at any other time. During the upcoming perigee on June 23 the Moon will be right around 221,824 miles away from us. That’s compared to 252,581 or so miles away that it’s at when it’s farthest distance from the Earth — the apogee.
With regards to the common rumors that tend to accompany upcoming Supermoons — while they certainly do create uncommonly strong tides, the tides are nothing very extreme. What can expect to see are tides that are a couple of inches higher and lower than those seen during regular Full Moons. With regards to the Supermoon causing earthquakes or volcanic eruptions — the jury is still out but there is no evidence that they do, Supermoons are a common occurrence and very rarely match up with irregularly strong earthquakes or eruptions.
Make sure to check out the other amazing astronomical events of 2013: Astronomy 2013 — Comet ISON, Perseids, Supermoon, Geminids, Solar Eclipses, Super Venus, Etc
An interesting note — while the Moon currently orbits at a distance of between 225,623 and 252,088 miles — it was previously much, much closer to the Earth, and has been slowly moving away. It is currently moving away from the Earth at a rate of about 1.5 inches a year.
Something else to note — as a result of the Moon moving away from the Earth — the two celestial bodies are slowly slowing one another down. The length of a day is currently growing by about 1/500th of a second every century.