Astronomy Picture of the Day

Explanation: What was so super about Wednesday's supermoon? Last week, a full moon occurred that appeared slightly larger and brighter than usual. The reason is that the Moon's fully illuminated phase occurred within a short time from perigee - when the Moon was its closest to the Earth in its elliptical orbit. Although the precise conditions that define a supermoon vary, last Wednesday's supermoon was surely the closest, largest, and brightest full moon this year. One reason supermoons are popular is because they are so easy to see -- just go outside at sunset and watch an impressive full moon rise! Pictured here, Wednesday's supermoon is compared to April's micro moon -- when a full Moon occurs near the furthest part of the Moon's orbit -- so that it appears slightly smaller and dimmer than usual. Given many definitions, at least one supermoon occurs each year, with another one coming next month (moon-th).