Blood Moon: NASA explains why the Moon turns red during Lunar Eclipse

The last total lunar eclipse of 2022 is expected to be seen on Tuesday and according to NASA, there will not be another full lunar eclipse until 2025 while there would still be partial and penumbral lunar eclipses during this period. During the eclipse on Tuesday, people will be able to witness the ice giant planet Uranus in the sky as the dim moon will pave the way for other celestial bodies to shine brighter.

Why Moon Turns Red During Lunar Eclipse?

According to NASA, 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.

Notably, the moon turns red during a lunar eclipse due to the same phenomenon that makes our sky blue and our sunsets red. According to NASA, it is called Rayleigh scattering.

As 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. 

Explaining why the moon turns red during a lunar eclipse, NASA said that red light 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.

Notably, during a lunar eclipse, the Moon turns red because the only sunlight reaching the Moon passes through Earth's atmosphere. The Moon gets redder when there are more dust particles or clouds in Earth's atmosphere during the eclipse. 

Image: Earth’s atmosphere scattering sunlight. The blue light from the Sun scatters away, and longer-wavelength red, orange, and yellow light pass through, turning the Moon red. Source: NASA  Science

Where to watch Lunar Eclipse?

As numerous organizations and individuals around the globe present live streams and videos of lunar eclipses, people can watch the lunar eclipse on Tuesday from their computer screens. Visit NASA’s Dial-a-Moon for a visualization of the eclipse.

How to observe Lunar Eclipse?

The lunar eclipse can be watched through the naked eye. Although binoculars or a telescope will enhance the view and the red colour. 

The "Blood Moon" will be visible for approximately 85 minutes from North America, parts of South America, Asia, Australia, and New Zealand. This is will be the second and last Lunar Eclipse or Chandra Grahan of 2022. 

On November 8, a partial lunar eclipse is expected to take place at 4:44 am EST (2:14 pm IST). The total eclipse phase, also known as Blood Moon, is expected to take place about an hour later at 05:17 am EST (2:47 pm IST) on the same day. The eclipse will be at its peak at 4:29 pm IST and will end at 6:42 am EST (4:12 pm IST).