A total lunar eclipse illuminated a "blood moon" in the night sky Thursday night and into Friday morning. The moon shifted from its regular bright white appearance to a deep rusty red, creating a phenomenal display. >> Scroll down for photosWhat's a lunar eclipse?A lunar eclipse occurs when the Earth lies directly between the sun and the moon. According to NASA, in a total lunar eclipse, the moon moves into the inner part of Earth's shadow, also known as the umbra.Once the moon is entirely within the umbra, it takes on a reddish-orange color.Photos: March 13-14 lunar eclipseWhat causes the moon to appear red during a lunar eclipse?The moon looks red during a lunar eclipse because of a process known as Rayleigh scattering. NASA explained this is the same process that causes the skies to turn blue and sunsets red.When sunlight goes through the Earth's atmosphere, the shorter blue light gets scattered away, while the longer red light is able to reach the moon, according to NASA. This gives the moon a reddish color, which is often called a "blood moon."