On 7 September there will be a total lunar eclipse as the Moon rises above the eastern horizon.
A lunar eclipse occurs when the Earth is positioned between the Sun and the full moon.
The Earth’s shadow falls upon the Moon, causing the Moon to dim and turn red/orange, which is why it is sometimes called a Blood Moon.
Although the Earth blocks direct sunlight, some of the light that passes through the Earth’s atmosphere still reaches the lunar surface. However, this light is scattered by clouds and dust, and the shorter wavelengths such as blues and violets scatter more easily, while longer wavelengths like reds and oranges make it through and illuminate the lunar surface. The more dust or clouds in Earth’s atmosphere, the redder the Moon appears.
The lunar eclipse will be visible from totality onwards.
The Moon will be fully above the horizon at 19:46 when the eclipse reaches its maximum. However, it will only be at an altitude of 0.9 degrees and civil twilight will only just have begun, so it might be tricky to see at this point, but will become clearer as the Moon rises and the sky darkens.
At 19:52 totality will end and the Moon will have risen slightly to 1.8 degrees altitude. The waning partial phases of the eclipse continue until 20:56, by which time the Moon will be at an altitude of 11.4 degrees and the night sky will have darkened to astronomical twilight. When looking towards the eastern horizon, you should also see the planet Saturn rising at about 20:30.
The moon is a familiar sight to us in the night sky. It is likely that it was formed from a collision between a young Earth and a smaller protoplanet called Theia, which was about the size of the planet Mars. A collision between two planet-sized objects would have been quite spectacular and could have ended up with both planets being destroyed. However, fortunately for us, this was not the case. What likely happened is that the two bodies collided with such force that they melted and reformed together as one, with a smaller part of the body spinning off to become the Moon.
The existence of the Moon has influenced the Earth considerably. Having a large body orbiting around our planet has stabilised the tilt of the Earth’s polar axis, resulting in more stable seasons and climate. In addition, the Moon’s gravitational pull creates the tides which play a crucial role in distributing heat, nutrients and oxygen throughout the oceans, keeping the planet and oceans habitable. The ebb and flow of the tide also creates an inter-tidal zone which is a hugely important part of our shoreline, providing homes and food for species both above and below the water, in addition to providing breeding grounds and nurseries for marine life.
Dr Jean Dean, FRAS