The penumbral eclipse arrives less than one month after the Sun briefly vanished behind the Moon on December 26 – an annular eclipse. The roles will reverse next week and this time the Moon will dip in brightness but without disappearing completely.
What is a penumbral eclipse of the Moon?
Lunar eclipses can be divided into three categories: total lunar eclipse, partial lunar eclipses and penumbral lunar eclipses.
During a total eclipse, the Moon completely enters the darkest shadow cast by Earth – the umbral shadow or umbra.
During a partial eclipse, only a fragment of the Moon dips into the umbra and a portion of the Moon appears to temporarily vanish.
A penumbral eclipse happens when the Moon passes through the faint, outer region of Earth’s shadow known as the penumbra.
However, all three events only occur when the Moon is fully illuminated by the Sun – the Full Moon phase of the lunar cycle.
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When is the first penumbral eclipse of 2020?
The penumbral eclipse coincides with the January Full Moon, also known as the Wolf Moon.
The Wolf Moon will peak on the evening of Friday, January 10, and the eclipse will begin just a few hours before it.
In 2019, there were three solar eclipses and just two lunar eclipses.
The last lunar eclipse fell on July 16 and was a partial eclipse of the Moon.
Before that, on January 21, a breathtaking Blood Moon eclipse turned the Moon a deep orange hue.
US space agency NASA said: “A lunar eclipse occurs when the Moon passes through Earth’s shadow just as a solar eclipse occurs when part of the Earth passes through the Moon’s shadow.
There is never a dark bite taken out of the Moon, as in a partial eclipse.
“But the Moon circles the Earth every month as it cycles through its phases, lining up at both Full Moon and New Moon.
“So why don’t eclipses happen twice a month? The reason is that the Moon’s orbit around the Earth is titled relative to the Earth’s orbit around the Sun.”
The Moon’s tilt changes over the year in respect to the Sun, which places it twice a year in a position to cross Earth’s shadow.
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When can you see the lunar eclipse next week?
The penumbral eclipse will unfold in the nightside of Earth, peaking over the UK in the evening hours.
Eclipsing will start around 5.07pm GMT when the Moon first enters the penumbra.
At this stage, you might not see any significant change in the Moon’s face.
Maximum eclipse, or when the Moon is nearest to the centre of the Earth’s shadow, will peak around 7.10pm GMT.
The spectacle will then wrap up around 9.12pm GMT on Friday.
Because the penumbral eclipse is considerably weaker than the umbra, penumbral eclipses might be hard to see with the naked eye.
Astronomer Deborah Byrd of EarthSky.org said: “This third kind of lunar eclipse is much more subtle, and much more difficult to observe, than either a total or partial eclipse of the Moon.
“There is never a dark bite taken out of the Moon, as in a partial eclipse.
“The eclipse never progresses to reach the dramatic minutes of totality.
“At best, at mid-eclipse, very observant people will notice a dark shading on the Moon’s face. Others will look and notice nothing at all.”