Depending on your location, many will be treated to a total eclipse of the Moon either tonight or during the early hours of tomorrow morning. What’s more, the spectacle occurs around the time when our lunar companion is at its closest point to Earth, causing the blood red moon to be slightly larger than usual.
The total lunar eclipse will be visible from most of North America and all of South America tonight just after sunset, eastern South America and Greenland will witness the greatest eclipse around midnight, while those in Europe, Africa and the Middle East will experience the total eclipse during the early hours of tomorrow morning. A partial lunar eclipse can be seen after sunset this evening from western Alaska or before sunrise in far-western Asia. You can find out the exact timings of the eclipse for your location here.
Weather permitting, this particular eclipse promises to be a grand one since it occurs when the Moon is very near the ‘supermoon’ point of its orbit where it’s at its closest to Earth (called perigee). The closest lunar perigee of the year occurs just 59 minutes before mid-eclipse, meaning that the Moon will appear up to 14 per cent larger in diameter.
A lunar eclipse happens when the Sun, Earth, and Moon form a near-perfect lineup in space. The Moon gradually glides into Earth’s shadow, until the entire lunar surface turns from white to an eerie dim orange or red. You only need your eyes to see the drama unfold, but if you have binoculars or a backyard telescope, these will give a much-enhanced view.
What can I expect to see?
A total lunar eclipse has five stages, with different things to watch out for at each.
The first penumbral stage begins when the Moon’s leading edge enters the pale outer fringe of Earth’s shadow: the penumbra. However, at this stage, the shading is so weak that you won’t see anything until the Moon is about halfway across it.
During the second stage we move into a partial eclipse. This begins much more dramatically when the Moon’s leading edge enters the umbra – Earth’s inner shadow where the Sun is completely hidden. With a telescope, you can watch the edge of the umbra slowly engulfing one lunar feature after another, as the entire sky begins to grow darker. The partial phase will last just over an hour. As its end approaches, only a final bright sliver remains outside the umbra. By this time the rest should already be showing a dim, foreboding reddish glow.
The third stage is a total eclipse, beginning when the last rim of Moon slips into the umbra. But the Moon won’t black out – it’s sure to glow some shade of intense orange or red. The red light you see on the Moon is sunlight that has skimmed and bent through Earth’s atmosphere and then continued on through space to the lunar surface.
If you picture it from the point of view of an astronaut standing on the Moon, they would see the dark Earth in the sky thinly ringed with brilliant orange from the Sun hidden behind it. The ring is bright enough to illuminate the lunar landscape with an eerie red
The red umbral glow can be quite different from one eclipse to the next. Two main factors affect its brightness and colour. The first is simply how deeply the Moon goes into the umbra as it passes through – the centre of the umbra is much darker than its edges.
The other factor is the state of Earth’s atmosphere along the sunrise-sunset line. If the air is very clear, the eclipse is bright. But if there is pollution in the Earth atmosphere taking the form of a thin global haze, a lunar eclipse will be dark red, ashen brown, or almost black.
In addition, blue light is refracted through Earth’s clear, ozone-rich upper atmosphere above the thicker layers that produce the red sunrise-sunset colours. This ozone-blue light tints the Moon also, especially near the umbra’s edge. The result can be a subtle mix of changing blue, grey, and even green.
And then, as the Moon continues along its orbit, events replay in reverse order. The Moon’s edge re-emerges into sunlight, ending totality and beginning stage four: a partial eclipse again.
When all of the Moon escapes the umbra, only the last, penumbral shading is left for stage five. By about 30 or 40 minutes later, nothing unusual remains.
The ‘super blood moon’ provides an exciting opportunity for astrophotographers, so don’t forget to send your images you manage to capture to firstname.lastname@example.org for a chance to be featured in the print edition of All About Space magazine!
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