25 July 2018 by Patrick Kiernan
This Friday 27 July we get the chance to see one of the wonders of the night sky: a total eclipse of the moon!
There are many different types of eclipses, including eclipses of the sun and eclipses of the Moon.
An eclipse of the sun happens when the Moon passes between the Earth and the sun and blocks the light from the sun. Sometimes the whole sun is covered (a total eclipse); sometimes only a part of the sun is covered, known as a partial eclipse. These are seen only over a very small part of the Earth at any time; the last total eclipse of the sun seen in the UK was in 1999 and the next one visible from the UK won’t be until August 2026.
An eclipse of the moon happens when the moon enters the Earth’s shadow. The moon does not make its own light but reflects light from the sun. It is often possible to watch Earth’s shadow sweep across the surface of the moon and then away.
As the shadow begins to cover the moon the moon begins to look different; it begins to turn reddish. The moon is not changing but the sunlight is being bent by our atmosphere and only the slower redder wavelengths of light pass through – causing the reddish tinge.
Friday’s eclipse happens when the moon is at its closest approach to the Earth for this month, making this the longest lunar eclipse of the century; lasting 103 minutes. Sadly we won’t get to see all the eclipse as the Moon doesn’t rise for us until 9:06pm, when the eclipse is in full swing. Totality is at 9:21 so the Moon will be very low in the sky. The eclipse ends around 12:28am (twenty eight minutes after midnight, when the moon will be reasonably high.
If you can, go somewhere with a clear eastern horizon so you can see the moon as soon as it rises. You might also notice below the moon a bright red ‘star’. This is Mars, the Red Planet. It is at its brightest right now as it lies directly opposite the sun (astronomers call this ‘Opposition’) so it is reflecting nearly all the sunlight that falls upon it.
If you can get to see Mars and the blood moon you are in for a treat. Best of all, the only special equipment you need is your eyes!
Want to learn more about Earth and its universe? Visit our Planetarium for a spectacular journey through space and time!
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