Updated at 11 a.m. ET
Get ready for a very rare event tonight — a blue moon.
But don't expect to see a new hue. A blue moon, at least according to the modern definition of the term, has nothing to do with color. It simply means a second full moon in the same calendar month.
As NASA explains in the video above: "Most blue moons appear pale gray and white, just like the moon you've seen on any other night."