Blue Moon Alert: See August's 2nd Full Moon

Inspired by the nearly-full moon, space station astronauts used an 800 mm lens to study the craters and mare in this picture taken on Oct. 5, 2001. CREDIT: NASA View full size image

The night skies this week have been very bright thanks to the moon, and they'll get brighter still on Friday as a blue moon rises above the horizon.

The moon won't literally be blue-colored, of course; the name refers to the second full moon to occur in a single month.

Blue moons happen because our calendar months don't line up exactly with the moon's orbit. It takes the moon 29.5 days to wax and wane from full to new to full again. With the exception of February, months are longer than that, meaning that every so often the timing works out so there are two full moons in one month.

The first full moon of August 2012 graced night skies on Aug. 1; for most of the world, the second just squeezes in at the end of the month, with the moon becoming full at exactly 9:58 a.m. Eastern Daylight Time (6:58 a.m. Pacific Standard Time).

Though a blue moon looks the same as any other full moon, the moon can actually appear to be colored under particular atmospheric conditions: Forest fires and volcanic eruptions can pump smoke and ash into the atmosphere, which can make the moon appear a bluish hue to those standing on the Earth's surface.

This week's blue moon will be the last until 2015, so take a look while you can!

For more skywatching information, check out sister site SPACE.com's Night Sky page.