IN THE EARLY hours of the morning tonight, our Moon will pass throw the shadow cast by Earth. This is known as a lunar eclipse, and this particular event will be the last in the current group of four eclipses, which have been taking place since April last year.

Weather permitting, we in Ireland will be in a great position to see the eclipse from start to finish.

An eclipse occurs when the shadow of one celestial body is cast onto another. The most familiar type of eclipse is the solar eclipse, where the moon is positioned between the earth and the sun, and its shadow is cast onto the earth.

Deep red glow

We saw this most recently back in March where we got to see a partial solar eclipse from Ireland. The moon can also be positioned on the other side of Earth, so that the Earth is in between the Sun and moon. This causes Earth’s shadow to fall on the moon, plunging it not into complete darkness, but into a deep blood red glow.

We usually think of shadows being dark, and not red, right? That’s because in our everyday experiences we don’t deal with giant planets with atmospheres. You’ll notice that at sunset the sky can appear red: this is because dust in the atmosphere scatters blue light away, and lets mostly red light through.

It’s this red light that passes through the atmosphere of our planet, bending through the air, and finally landing on the moon, giving it a red colour during an eclipse.

In for a treat  

If you’ve never seen a total lunar eclipse before, then you’re in for a treat: it’s quite like nothing you’ve ever seen before. When you look at a full moon on a normal night you’ll notice that it’s very bright. You’ll see some features on its surface, but overall it looks kind of “flat”.

During a total eclipse, however, the moon is much dimmer because it’s in shade. This makes it easier to see the lunar maria and vast impact craters on its surface. Not only that, but the shadow itself has a slight gradient consisting of different shades of red.

Shutterstock / muratart Shutterstock / muratart / muratart

This gradual change of colour really brings out a three-dimensional feel to the moon, and you can actually see it as a sphere, rather than the usual “flat” moon we’re used to seeing.

Before they were fully understood, lunar eclipses have had an influence on historical events. In the early 1500s Christopher Columbus’s sailors were stealing goods from the native Jamaicans, despite the natives supplying food to the voyagers.

In retaliation, the Jamaicans halted the food supply. Columbus had with him an astronomical almanac detailing the dates and times of various astronomical events, and he knew there was a lunar eclipse coming up. He demanded to meet with the leader of the indigenous people, and told him that his god was angry with the people of Jamaica for halting the supplies. So angry, in fact, that the god would turn the moon red.

Lo and behold, the eclipse began, the moon turned red, and the people of Jamaica immediately began providing supplies again. Columbus knew the duration of the eclipse, too, so as the eclipse drew to an end, he told the native people that they were to be forgiven by his god.

This month’s eclipse begins at about 1:10am Irish time on 28 September and from then you’ll gradually see a dark shadow move across the moon. At about 2:45am you’ll see the red colour appear, and at 3:45am the eclipse will be in its deepest phase, with the moon bathed in red.

From there, the moon will move out of Earth’s shadow, and the whole eclipse will be over by 6:20am.

This all happens early on Monday morning (or very late Sunday night, if you’re a night owl!) so the time’s are not ideal for a “school night”. However, it really is a sight to behold so it’ll be worth getting up for a short while to check it out, as the next total lunar eclipse with a red shadow won’t be visible from Ireland until 2019.

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