Total Lunar Eclipse, 21 January, Sun - Mon night
This is the first TLE to be entirely visible from Ireland since 28 Sep 2015. The next one where the total phase is even partly visible from here will be on 16 May, 2022, but the Moon sets during the total phase of the eclipse.
A Total Lunar Eclipse (TLE) occurs when the Moon passes into the shadow of the Earth in space. It can only happen at Full Moon, because obviously the Earth's shadow must lie opposite to the Sun. We don't get an eclipse every Full Moon because the Moon's orbit is tilted at an angle of over 5º to the Earth's orbit, so usually the Moon passes above or below the shadow.
WOLF? BLOOD? SUPER?
There is a lot of hype about this being a 'Wolf Blood Super Moon', or some other combination thereof. The operative word there is 'hype'. The 'Wolf' bit is from the Native American name for the Full Moon in January. The only wolves here are in the zoos, so we can forget that bit.
The Blood bit refers to the fact that the Moon turns reddish during a TLE, because the only sunlight reaching it has passed through the Earth's atmosphere, which filters out most other colours apart from red and orange. However it's very rare for it to turn blood red – see below. More hype.
And the Super bit refers to the fact that this one occurs when the Moon is fairly close to Earth, and so appears a bit bigger than usual. But it's only the third closest Moon of the year, so you would hardly notice that it was any bigger than usual. More hype!
However, it will quite a long eclipse, with 1h 3m of totality. The Moon will be quite high up for all the major stages of the eclipse: 48º up at the start, and still 14º above the horizon at the end of the main shadow stage. First contact of the Earth's shadow will be about SE on the Moon's disc.
The Moon will pass North of the centre of the Earth's shadow, so if you look carefully, even at mid-eclipse, the N edge of the moon will be less darkened than the S edge.
WHAT WILL WE SEE?
One of the interesting things about TLEs is that no-one knows in advance just what they will look like. The Moon can turn anywhere from a bright orange-red to a deep almost crimson/grey red: it all depends on the amount of dust and dirt and aerosols in our upper atmosphere, through which sunlight passes to reach the Moon.
The eclipse will start at 02 35 when the Moon enters the faint outer part of the shadow, but this is barely noticeable
It starts to enter the main shadow at 03.33, when you'll notice a darkening on the SE edge of the Moon.
The whole of the Moon will have entered the dark main shadow at 04.40, which marks the start of total eclipse, and the maximum eclipse will be at 05.12.
It will start to exit from the main dark shadow at 05.33, so that's the end of totality, and the Moon will completely exit the main shadow at 06.51.
WATCHING THE ECLIPSE. If you only start looking during totality, and the eclipse is a dark one, you may not immediately be able to see the Moon, especially if you are viewing from a town or city! During the total phases, the Moon will be in the SW part of the sky - roughly where the summer Sun would be in mid-afternoon..
Look for the changing colour of the Moon as it slips deeper into the shadow, and then moves out the other side.
If you are lucky enough to be able to see the whole event, you can get a mental picture of the size of the Earth's shadow at the distance of the Moon by watching the Moon move against background stars. After the start of the eclipse at about 03 15, the Moon will be in almost exactly a straight line drawn from Castor through Pollux, the two brightest stars in Gemini, which will lie to the upper right of the Moon. By the end of the main stage at 06 51, the Moon will be well past that line, so you can see just how far it has moved. However, the Earth's shadow is even bigger than that, because the Moon does not pass through the centre of the shadow, as noted above!
You don't need any optical aid to observe the eclipse, but binoculars will give a nice view of the changing colours as the eclipse develops.
For more information see: www.irishastro.org
NOTES TO EDITORS:
1. The Irish Astronomical Association is a registered charity dedicated to promoting interest in, and information about, astronomy and space and related topics. It is the oldest and largest astronomical society based in N. Ireland, and the largest amateur astronomy society in Ireland.
2. An eclipse happens when the Sun, Earth and Moon line up exactly in a straight line. If this happens at new Moon we get a Total Solar Eclipse, and if at Full Moon, we get a Total Lunar Eclipse.
3. The eclipse occurs in the early morning of 21 January, so that's Sunday/Monday night.
4. The next fairly good Total Lunar Eclipse for us will be on 31 Dec 2028, when the Moon has just risen at the start of totality, so we'll see most of that one.
But the next TLE which is entirely visible from here won't be until 20 Dec 2029! So let's hope for a clear night, and make the most of it since it's a long time to the next one!
5. Astronomers use the DANJON SCALE to describe the darkness of TLEs.
0. = Very dark, Moon almost invisible.
1. = Dark, grey or brownish colour; details barely identifiable
2. = Dark or rusty red, with a dark patch in the middle of the shadow; brighter edges.
3. = Brick-red, sometimes a bright or yellowish border to the shadow.
4. = Coppery or orange-red, very bright, with a bluish cast and varied hues.
6.PRECISE TIMES
Moon enters penumbra 02h 34m 43s
Moon enters umbra 03h 33m 16s
Start of totality 04h 40m 30s
Maximum eclipse 05h 11m 59s
End of totality 05h 43m 30s
Moon leaves umbra 06h 50m 44s
Moon leaves penumbra 07h 49m 15s.
7. The IAA runs public events throughout the year, including free public lectures at QUB, and public outreach events in various locations throughout Northern Ireland, details of which are available on the website: www.irishastro.org
Terry Moseley
PR Officer
Irish Astronomical Association
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