On the evening of 20/21 January 2019 there can be a complete eclipse of the Moon, which can be viewable from many areas of the world. This can be value making the hassle to see, particularly for my readers within the western USA and Canada for whom it should happen at a sociable hour.
The Moon throughout a latest complete lunar eclipse – picture from NASA
What occurs throughout a lunar eclipse?
A lunar eclipse happens when the Earth prevents some or the entire Solar’s mild from hitting the Moon’s floor. That is proven within the diagram beneath:
Picture from Wikimedia Commons
On this diagram:
- within the area marked umbra the Earth utterly blocks the Solar from hitting any of the Moon’s floor
- Within the area marked penumbra the Earth partially blocks the Solar.
The levels of the January 21 lunar eclipse
The following diagram beneath exhibits how the Moon will transfer by the Earth’s shadow on 21 January. The six factors labelled P1, U1, U2, U3, U4 and P4 are often called the eclipse contacts and are the occasions when the eclipse strikes from one stage to the subsequent
(Tailored by the Science Geek from a NASA diagram)
At level P1 the Earth will begin to block a number of the Solar’s mild from reaching the Moon. This will begin at 2:37 AM GMT(UTC) and is the start of the penumbral part. At this level the Moon’s brightness will dim a little bit, however this can be fairly troublesome to note with the bare eye.
Because the Moon continues in its orbit, increasingly more of the Solar’s mild is obscured, till after about an hour some areas on the Moon will get no direct daylight. This is named the partial part. It would begin at level U1 which happens at three:34 AM GMT. The a part of the Moon which receives no direct daylight will seem darkish, as proven within the image beneath.
The partial part of a lunar eclipse – Picture from Wikimedia Commons
After an extra hour the Earth will block all direct daylight from reaching the complete Moon. That is proven as U2 is the diagram and this complete part will begin at four:41 AM Within the complete part, slightly than disappearing utterly, the Moon goes a boring pink color as proven within the image on the high of this submit. It is because, regardless that no direct daylight can attain the Moon, some mild from the Solar is bent around the Earth’s ambiance in the direction of the Moon. This mild seems pink as a result of seen mild from the Solar is a mix of various wavelengths – pink mild has the longest wavelength and violet the shortest. A lot of the mild of the shorter wavelengths (orange, yellow, inexperienced, blue, indigo and violet) is faraway from this mild bent by the Earth’s ambiance by a course of known as scattering, which I mentioned in an earlier submit https://thesciencegeek.org/2015/09/30/why-is-the-sky-blue/ . The identical impact causes the western sky to be pink after sundown on a transparent day.
Curiously, if we might stand on the floor of the Moon throughout the eclipse we might see a pink ring across the Earth.
The Moon will emerge from the whole part (level U3) at 5:43 AM, the partial part (level U4) will finish at 06:51 PM and the eclipse will end (P4) at 07:48 PM.
The eclipse timings are summarised beneath
Knowledge from NASA (2009)
The place can the eclipse be seen
Not all areas of the world will have the ability to see the complete eclipse. It is because the Moon may have already set after the eclipse begins or won’t have risen earlier than it finishes. Different locations on this planet will solely have the ability to see a part of the eclipse.
- In Manchester, the place Mrs Geek and I reside, the Moon will rise at 15:41 native time (GMT) on the afternoon of January 20 and set at 08:25 the next morning. So will probably be above the horizon for the complete eclipse, Nonetheless, we might want to keep up late or rise up very early to see it 😉
- In Warsaw, Poland the Moon will rise at 15:10 native time (UTC+1) on January 20 and set at 07:48 the next morning. So viewers will miss a part of the ultimate partial part and the entire ultimate penumbral part as a result of these will happen after the Moon has set.
- In San Francisco, California, which is eight hours behind UTC the complete eclipse can be viewable and can happen on the night of 20 January.
I’ve tailored the diagram beneath from NASA (2009) and this exhibits the place on this planet the eclipse could be seen.
The areas labelled A to L are as follows
How typically do lunar eclipses happen?
Though the Moon takes roughly a month to orbit the Earth, lunar eclipses don’t happen each month. The Moon’s orbit across the Earth is tilted at about 5 levels with respect to the Earth’s orbit across the Solar, as proven beneath.
Which means throughout most lunar months, as seen from the Moon, the Earth passes slightly below or simply above the Solar slightly than obscuring it. There are solely two time home windows in a 12 months when a lunar eclipse can happen. These two factors are often called the nodes (See be aware 2). Even then most lunar eclipses are partial eclipses the place the Earth solely partially covers the Moon.
- GMT versus UTC
Though the time period Greenwich Imply Time (GMT) is usually utilized in in style writing it’s not utilized by astronomers. As a substitute, they use two completely different occasions which agree with one another to inside 1 second.
- Common Time, typically abbreviated to UT1, is the imply photo voltaic time, the time decided by the rising and setting of the Solar on the Greenwich Meridian, zero levels longitude.
- Co-ordinated Common Time, normally abbreviated to UTC, is the time measured by atomic clocks and is stored to inside 1 second of UT1 by the addition of leap seconds.
In widespread use, GMT is usually taken to be the identical as UTC, which is the method I’ve taken for this submit. Nonetheless, it can be taken to imply UT1. Owing to the paradox of whether or not UTC or UT1 is supposed, and since timekeeping legal guidelines normally consult with UTC, the time period GMT is often prevented in exact writing.
- Nodes when eclipses can happen
The 2 nodes when a lunar eclipse can happen aren’t the identical dates yearly however change from 12 months to 12 months resulting from an astronomical impact known as precession of the road of nodes.
NASA (2009) Complete lunar eclipse of 2018 July 2017, Out there at https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2019Jan21T.pdf (Accessed 1 January 2019)
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