From National Geographic Space Pictures This Week; June 28, 2013:
Supermoon Over D.C. Bill Ingalls, NASA
The beauty of Earth’s closest companion was on full display as the largest and brightest full moon of the year rose above the Washington Monument in Washington, D.C., on June 23. (See supermoon pictures submitted to National Geographic’s Your Shot.)
Known popularly as a supermoon—or perigee full moon—this phenomenon occurs when the moon reaches its closest distance to our planet while coinciding with a full phase.
Because the moon’s orbit is elliptical, there are certain times the moon can be closer (at perigee) or farther (apogee) from our planet, making its apparent diameter appear larger and brighter or smaller and fainter than usual. (Read the full story of this year’s supermoon.)
For this year’s closest perigee, the moon appeared 8 percent larger and 17 percent brighter than usual, while approaching our planet at a distance of 221,823 miles (356,991 kilometers). That’s a bit closer than the typical 238,885-mile (384,400-kilometer) distance.
In 2011, the so-called supermoon was the closest it’s been in two decades—only 221,565 miles (356,575 kilometers) from Earth.