In the early hours of the morning on Monday 28 September we will be treated to a rare coincidence of two lunar phenomena; a supermoon and a total lunar eclipse.
Image Credit: NASA
The Moon’s orbit around the Earth is not a perfect circle but instead takes on the path of a slightly squashed circle – an ellipse. This eliptical orbit means that the distance of the Moon from the Earth changes as it loops around our planet. At its closest approach (perigee) the Moon resides around 363,000 kilometres from the Earth whilst at the furthest point (apogee) it sits at 406,000 kilometres. A supermoon occurs when the Moon is at perigee making it appear brighter and bigger in the sky with the apparent diametre appearing as up to 14% larger. There are normally around 4-6 supermoons in a year.
Total Lunar Eclipse
A total lunar eclipse occurs when the path of the Earth brings it directly between the Sun and the Moon, blocking the Sun’s light. We are only able to see the Moon because its surface is able to reflect the Sun’s light.
As the Earth’s shadow moves across the Moon we experience an eclipse; a total lunar eclipse only occurs when the Earth’s shadow completely covers the Moon. It might be expected at this point that the Moon might disappear entirely when instead what we see is that the Moon turns red giving it its name as a ‘blood moon’. This happens because as sunlight passes close by the Earth it is bent inwards and is able to illuminate the Moon’s surface. The bright red hue occurs because of the way light is changed as it passes through the atmosphere of the Earth as it passes.
Supermoon Lunar Eclipse
The coincidence of these events hints for a spectacular show early Monday morning. The last time that these two events occurred together was back in 1982 and we will have to wait until 2033 to witness it again. This event is also interesting as it marks the last of four lunar eclipses in a two year time period, scientifically known as a lunar tetrad. The UK is lucky enough to lie within the path of totality, alongside the Americas, the west of Africa and parts of Europe, and so will be able to witness the full event.
From start to finish the eclipse will last for hours but the time of the total eclipse will last for a little over one hour. The partial eclipse will begin at around 2:00 am but it won’t be until 3:00 am that the total eclipse begins.Nothing special is needed to view the supermoon lunar eclipse but you will need to wish for good weather and do your best to stay awake until the early hours to see this fascinating sight.