This month's full moon is a "blue" one by one definition, but not according to the traditional definition of a blue moon.
The moon will be full at 6:43 a.m. Friday, so it will be at its brightest in our night sky Thursday night into Friday morning. July's full moon is known as the Buck Moon or the Thunder Moon.
Because it is the second full moon this month -- the first was July 1 -- it can be considered a blue moon under the modern definition of the term. That definition can be traced to a Sky and Telescope magazine article from 1946, a children's almanac in 1985, and the game Trivial Pursuit, according to EarthSky.org.
But the traditional definition was always the third full moon in a season that contained four full moons. A normal season contains three full moons, of course, each with a name appropriate for the time of year. (In July, thunder is common, of course, and it's also when bucks often begin to grow antlers.) So when a fourth full moon appears in a season, it disrupts those naming conventions.
Friday is an inopportune time for a full moon in one sense because it will outshine the Delta Aquarid meteor shower, which peaks in late July. But the timing also means the moon will be a thin crescent by the time the more dramatic Perseid meteors peak Aug. 11 and 12.