The moon will turn red in the night sky tonight in an event known as a blood moon.
The phenomenon only happens a handful of times a year, and this is your next chance to spot one in the UK.
A blood moon is a full lunar eclipse, occurring when the Earth passes between the moon and the sun.
From the UK, only a partial lunar eclipse will be visible, meaning only part of the moon will appear red.
But when is it, what exactly will you see, and what causes it? Here’s everything you need to know.
When is the blood moon?
Those who want to see it will have to get out of bed early tomorrow morning.
That’s because the eclipse will start to be visible at 3.57am, becoming particularly noticeable at 5.09am, according to the Royal Observatory Greenwich.
It says the maximum of the eclipse in London will be at 6.19am.
The full lunar eclipse will be at 6.58am UK time. But that will only be visible to people in North and South America, because in the UK the moon will already have set below the horizon.
What will you see?
At 3.57am, the moon will move into the Earth’s penumbra – the lighter part of its shadow – making parts of it appear dark, explains Imo Bell, astronomy education assistant at the Observatory.
Then at 5.09am, the part of the moon in shadow will turn reddish as the moon moves into the darker part of Earth’s shadow, known as the umbra.
How can I see it clearly?
The phenomenon will be clear with the naked eye, weather permitting.
You can give yourself the best possible chance of a good shot by getting a clear view of the western horizon from 5.09am, Bell says.
This will allow you to see the Earth’s shadow gradually cover the moon while it moves towards the horizon, before it sets after 6.19am.
“Wales, Northern Ireland, Cornwall and western parts of Scotland will be favourable because you want to delay the moon sinking below the horizon for as long as possible, so the more west, the better,” adds Bell, who describes their first blood moon experience, in 2008, as “magical”.
“My dad used mugs to explain how the sun, Earth, and moon would form a perfect line and then let us stay up way past bedtime to head out into the cold to watch the moon turn red,” Bell says.
What causes a blood moon?
It is caused by the Earth passing between the moon and the sun, known as a lunar eclipse.
During a total lunar eclipse, the Earth completely stops sunlight from directly hitting the moon as the sun and the Earth perfectly align with it.
Only light that is refracted through Earth’s atmosphere manages to reach the moon, with everything outside of the red wavelengths being scattered, leaving the moon looking blood red.
“This is due to the scattering of bluer hues in the sun’s light through our atmosphere, leaving only oranges and reds to reach the moon – the same reason we get reddish sunrises and sunsets,” Bell explains.
The UK is only catching a partial lunar eclipse, because the moon will only be visible while the sun, Earth and moon are almost aligned, rather than fully.
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How often is there a lunar eclipse – and when is the next one?
Because of the way the moon orbits the Earth, and because the Earth orbits the sun, there are always between two and five a year visible from somewhere on our planet, according to the Observatory.
This might make you wonder why there are not lunar eclipses every month as the moon orbits Earth.
It’s because the moon’s path is tilted compared to Earth’s orbit around the sun, moving up and down as it goes. This means it doesn’t always get in Earth’s shadow.
There will be an opportunity to see a total lunar eclipse in the UK on 7 September – though the view is expected to be challenging due to how low the moon will be on the horizon. There will be more information on that nearer the time.
In the meantime, we hope you get a good view tomorrow.
