Why Is the Moon Red?

Super Blue Blood Moon – this is a term coined by NASA for the celestial event many are witnessing across the world right now (or if you’re reading this later, on 31 Jan night).

Image result for blood moon

The last time it occurred was 1866 – 152 years ago. But what makes it so rare? And more importantly, how is the moon RED?

This Super Blue Blood Moon (let’s call it SBBM for short) occurs because of a trifecta of rare lunar events:

1) A blue moon – the second full moon in a calendar month

2) A super moon – the closest approach of the moon to the earth during a full moon (Singaporeans might associate this with the large full moon during 中秋节, or Mid-Autumn Festival)

3) A total lunar eclipse, where the moon is directly eclipsed by the earth’s shadow.

Image Source: NASA

Due to the eclipse, sunlight only reaches the moon by refracting through the Earth’s shadow. Apart from red light, the other wavelengths of light are absorbed by the Earth’s atmosphere. And as we all know, the moon reflects this light, giving it a reddish hue.

 The next blood moon will be in July 2018

In some ways, it is similar to how sunrises and sunsets are red – due to red light from sunlight ‘scattering’ around the earth at the horizon.

Enjoy the SBBM while it lasts! If you can’t see it physically, check out the live stream here! Or if you’re too late and have missed it already, check out the video recap here!

Some photos of the SBBM by astronomy enthusiasts in Singapore!

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