A total lunar eclipse graced the night skies Sunday providing longer than usual thrills for stargazers across North and South America, including Central Oregon.
The moon was bathed in the reflected red and orange hues of Earth’s sunsets and sunrises for about 1 1/2 hours. It was one of the longest totalities of the decade and the first so-called blood moon in a year.
For those who missed the show, NASA Science Live held a livestream event to talk about the phenomenon as it was happening. It can be seen in the player below.
What is a lunar eclipse?
A lunar eclipse occurs when the Sun, Earth, and Moon align so that the Moon passes into Earth’s shadow. In a total lunar eclipse, the entire Moon falls within the darkest part of Earth’s shadow, called the umbra. When the Moon is within the umbra, it will turn a reddish hue. Lunar eclipses are sometimes called “Blood Moons” because of this phenomenon.
Why does the Moon turn red during a lunar eclipse?
The same phenomenon that makes our sky blue and our sunsets red causes the Moon to turn red during a lunar eclipse. It’s called Rayleigh scattering. Light travels in waves, and different colors of light have different physical properties. Blue light has a shorter wavelength and is scattered more easily by particles in Earth’s atmosphere than red light, which has a longer wavelength.
Red light, on the other hand, travels more directly through the atmosphere. When the Sun is overhead, we see blue light throughout the sky. But when the Sun is setting, sunlight must pass through more atmosphere and travel farther before reaching our eyes. The blue light from the Sun scatters away, and longer-wavelength red, orange, and yellow light pass through.
During a lunar eclipse, the Moon turns red because the only sunlight reaching the Moon passes through Earth’s atmosphere. The more dust or clouds in Earth’s atmosphere during the eclipse, the redder the Moon will appear. It’s as if all the world’s sunrises and sunsets are projected onto the Moon.