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8th November Total Lunar Eclipse

Ever heard of, or even seen a “Blood Moon?’

Chances are, you have! It is more commonly known as a Total Lunar Eclipse and you will have a chance to see one on the 8th November between 6:30pm and 9:00pm AWST.

A Total Eclipse of the Moon (which is completely different to a Total Eclipse of the Heart) occurs when the Sun, Earth and Moon line up, this is called Syzygy (three “Y’s” – impressive!). But, I can hear you ask, doesn’t the Sun/Earth/Moon line up every month? Well, yeah, they do…..sort of.

The Moon’s orbit around Earth is tilted at ~5 degrees with respect to the ecliptic (the flat, race-track like plane of the Solar System where all the planets speed around the Sun).  Most of the time, the Earth’s shadow misses the Moon because it either falls above or below the Moon. However, when the Moon’s inclined orbit intersects the Ecliptic (called Nodes) this is when you have the Moon entering the shadow of Earth and, voila! A Total Lunar Eclipse!

Now, why does the Moon turn Red (hence the overly-dramatic Blood Moon name). We’ll, it’s the same reason why we have beautiful sunsets here on the West Coast.

It’s called Rayleigh Scattering. 

How this works is like this:

Light travels in waves, and different colours 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 because of this scattering. 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.

Ok, stick with me….. So the Red/ Orange/ Yellow wavelengths of light pass through Earth’s atmosphere and are scattered deep into Earth’s shadow, so when the Moon passes through Earth’s shadow, it doesn’t go completely dark because there is Red/ Orange/ Yellow light within the shadow area….. hence a Red/ Orange Moon (or a Blood Moon if you insist).

Total Lunar Eclipses are a fun reminder of the beautiful mechanics of our Solar System. The Total Lunar Eclipse on the 8th November will be a bit tricky to see initially. Firstly, the Moon will be in Totality (totally eclipsed) as it rises. The Sun will be setting as the Eclipsed Moon is rising, so observing the Eclipsed Moon may be difficult. However as dusk turns to night, our view will improve. The Moon won’t leave Totality until 7:42pm AWST, so you’ll have a chance to observe it.

The Gravity Discovery Centre Observatory Chief Astronomer, Rick Tonello, will be hosting a LIVE-SKY Astronomy broadcast from Mill Point in South Perth for the occasion. You can pop by and say “Hi!” and see the eclipsed Moon rising above the spectacular Perth City skyline!

You might even want to take a picture!