The year 2008 is a leap year, meaning we got an extra day last month, which, for some of our readers, was only yesterday.

In honor of the once-every-four-years event, NASA has compiled pictures of lunar eclipses since leap year 1996. There were 13 total lunar eclipses since 1996, and 11 of them are shown here.

One of the eclipses shown here is the most recent one from a a few days ago. The lone white moon in the picture comes from a partial lunar eclipse.

A lunar eclipse happens when the moon goes behind the Earth with respect to the Sun. You'd think that by doing this, the Moon won't be getting any sunlight. However, this isn't the case. What happens is that light gets refracted off the Earth's atmosphere, which hits the moon.

Because light only reaches it after being refracted from our atmosphere, colors with longer wavelengths will tend to persist. The result is that the Moon becomes red. It's the same thing that happens when the sky becomes red during sunrise and sunset.

The variations of the moon's size and color in NASA's picture is due to the distance of the Earth to the Moon at the time the picture was taken, and the amount of dust and cloud that light has to go through in the Earth's atmosphere before hitting the moon.