Full moon will appear red for a time during eclipse due to Rayleigh Scattering of light
The Beaver Moon lunar eclipse will begin at 7.18am on 19 November and last just over 6 hours. The sun’s arrival shortly after it begins means viewers in the UK will miss the peak of the eclipse, which begins at 9.02am and lasts for 3 hours and 28 minutes.
The peak of the Full Moon – known as the Beaver Moon as it traditionally coincides with Native American tribes setting their beaver traps – occurs at 8.57am GMT on Friday, but will appear full on both Thursday and Friday night.
Those in North and South America, as well as parts of East Asia, will have the best view of the full lunar eclipse.
It comes less than six months after the last partial lunar eclipse, which took place on 26 May, 2021. This week’s lunar eclipse falls just short of being a total eclipse with 97.4 per cent of the Moon’s diameter covered by the Earth’s shadow.
Only the southern-most edge will remain untouched by the shadow.
The Moon will actually appear slightly red during the lunar eclipse due to a process known as Rayleigh Scattering.
“The same phenomenon that makes our sky blue and our sunsets red causes the Moon to turn red during a lunar eclipse,” Nasa explains on its website.
“Light travels in waves, and different colours of light have different physical properties. Blue light has a shorter wavelength and is scattered more easily by particles in Earth’s atmosphere than red light, which has a longer wavelength.”
The US space agency continues: “Red light, on the other hand, travels more directly through the atmosphere. When the Sun is overhead, we see blue light throughout the sky. But when the Sun is setting, sunlight must pass through more atmosphere and travel farther before reaching our eyes.
“During a lunar eclipse, the Moon turns red because the only sunlight reaching the Moon passes through Earth’s atmosphere. The more dust or clouds in Earth’s atmosphere during the eclipse, the redder the Moon will appear.”
It is this effect that sometimes leads lunar eclipses to be known as “blood” moons.
Weather in the UK will be mostly clear on Thursday and Friday night, according to the forecast from the Met Office, though parts of the north and west will be shrouded in cloud and could miss the celestial spectacle.