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OUT OF THIS WORLD | What's New in Space – The Biggest News Arriving on Earth from Space
Scott Sutherland
Meteorologist / Scientific Editor
Thursday, July 5, 2018, 19:42 – By the end of July, the Moon will pass directly through the shadow of the Earth, producing a total lunar eclipse for parts of the world, and because of a whim of physics, it will be the longest eclipse in a century!
July 27, 2018 will be a busy night for astronomers and sky observers.
The full moon of July – known as "Full Thunder Moon", due to the storms often encountered during this month of the year or "Full Buck Moon" as it is the time of year when manly deer begin to fend off their antlers – will be accompanied by a very bright Mars, which will rise all night, while the Earth, Mars and the Sun align perfectly in an alignment known as the Opposition.
Large and bright March, with the Thunder Moon Mini, July 27. Saturn still bright will be visible to the southwest. Credit: Stellarium / Scott Sutherland
This Full Thunder Moon is remarkable in two different ways – 1) It is the longest and smallest full moon of 2018 and it will produce the longest total lunar eclipse that many will never see on Earth.
If you are at the right place in the world on the 27th, or if you are glued to your computer screen, look at one of the livestreams that will undoubtedly appear at the top, you will see the moon change color to match Mars because it passes directly through the deepest and darkest part of the Earth's shadow.
The path of the Moon through the shadow of the Earth on July 27, 2018. Source: NASA / Scott Sutherland
The moment of the eclipse is such that the the only part of Canada that will see part of it, in person, is the eastern half of the island of Newfoundland, just as the moon rises that night.
The visibility of the total lunar eclipse of July 27, 2018. Credit: Fred Espenak / NASA
It is doubtful whether anyone will notice, because only the dim light diffuse will cover the Moon at that time, which is very difficult to see.
The truly remarkable part of this eclipse, however: it will be the longest total lunar eclipse of this century !
From beginning to end, the time of the total lunar eclipse, where the moon will appear completely red, will last for 103 minutes – 1 hour and 43 minutes of totality. There was a longer one just 18 years ago, on July 19, 2000, which lasted 106 minutes. In the future, however, there is not another total lunar eclipse that is longer than this for the rest of this century, and in fact, until the end of the century. year 2123!
Why is this eclipse so long?
reasons why it is the longest lunar eclipse of the next century.
The relative distance, and therefore the apparent size of the Moon, plays an important role. The speed at which the Moon moves is another factor. Like the path that the Moon takes through the shadow of the Earth
The first three factors – distance, apparent size and speed – depend on the shape of the orbit of the Moon and of the Moon. along this orbit in relation to the Earth and the Sun.
As the moon revolves around the earth, it does not trace a perfect circle. Instead, his path is an ellipse, so he has the shape of an egg. Sometimes it's closer to the Earth. Sometimes it's further away.
Because of this form, each month, the Moon passes through its closest point to the Earth, known as the "1945-9010" perigee & # 39; At the furthest, it is in & # 39; climax & # 39 ;. The perigee can range from 356,400 km to 370,400 km, while the peak can be between 404,000 km and 406,700 km (the average distance of the Moon is about 384,400 km) [19659006Theperigeeandtheapogeevaryfrommonthtomonthgood
The ellipse of the orbit of the Moon around the Earth, for July 2018. The lunar perigee of July is the 13th, during the New Moon, at a distance of 357.431 km. The lunar climax of July is 27, during the full moon, at a distance of 406,222 km. Credit: NASA Goddard Scientific Visualization Studio / Scott Sutherland
Then there is the movement of the Moon along its orbit, as well as its movement with respect to the Earth and the Sun.
The Moon is exactly opposite of the Earth of the Sun. However, with each successive Full Moon, the Earth moved further into its own elliptical orbit around the Sun.
So, while it takes a little over 27 days for the Moon to complete a complete orbit around the Earth, at the same place where it was, the last time that it was full, in this moment, the Earth has changed orientation with respect to the Sun. Thus, when the Moon performs a sidereal orbit (as shown below), it is only almost full. It takes a little over two days of travel along its orbit before ending up in the right place in space to give us the next full moon (a synodic orbit).
The orbit of the Moon around the Earth, showing the difference between a sidereal orbit and a synodic orbit, revealing how the position of the Moon in its orbit progresses for each Full Moon. Credit: NASA Goddard Scientific Visualization Studio / Scott Sutherland
As shown in the animation above, this additional travel time places the Moon at a different location along its orbital ellipse for each Full Full successive. Earth. Since the orientation of the orbital ellipse remains relatively the same throughout the year, the Full Moons go through a cycle – getting closer and closer (and bigger and brighter) up to That we have our Full Moon . away (and smaller and weaker) until we see the full moon Apogee .
Back on January 2, 2018, we had seen Perigee Full Moon from 2018. While the lunar climax that followed immediately on January 15 was the farthest that the Moon will reach all year (406,459 km), which corresponds to the New Moon – when the Moon is on the same side of the Earth as the Sun. [19659006] The lunar climax of July 27 – the second lunar climax farthest from the year – takes place on the same night as the full moon. This makes it the apogee full moon this year.
Apogee Thunder Moon of July. On the left, the Moon reaches the apogee, at 406 228 km, at 06 UTC, while it is still at 99.9%. On the right, the Moon reaches 100% of its full capacity, about 16 hours later, but when the Moon is slightly closer to Earth. In the background, January 1 Perigee Supermoon is profiled in comparison. Credit: NASA GSVS / Scott Sutherland
With the full moon being so far away, it means that it will appear smaller than usual, and it will present a smaller face when 39, it crosses the shadow of the Earth . Thus, it will take less time to get completely in the shade, and thus spend more time crossing to get out of the other side. A closer, and therefore larger, Moon would occupy a larger area of shadow while traversing, so would spend less time, overall, completely covered by this part of the shadow.
There is also a "weirdness" to travel on an elliptical. orbits around a massive body like Earth. When you go through the climax, you move to your slowest speed in your orbit (your fastest speed is perigee).
Thus, with this full moon occurring at the climax, it is a full moon in slow motion. As a result, when the moon passes through the shadow of the Earth, it will do so at a very slow pace and will therefore take longer to traverse the dark – the deepest and darkest part of the Earth. 39, shadow of the Earth – until 2123
. The exact path of the Moon through the Shadow also comes into play here because the Shadow is a circle. Therefore, any path of totality closer to the center of this circle will result in spending more time in the shadow . If the moon follows a path of totality that passes through the shadow closer to the top or bottom of this circle, she will spend less time in the shadows.
The path of the totality of the total lunar eclipse of May 26, 2021. Since the path is very close to the northern end of the shadow, this total eclipse does not will last only 14 minutes. Credit: Fred Espenak / NASA
It is true that the ombra itself becomes narrower, the farther away from the Earth, and this has a small effect on the total time of crossing of the Moon. The cone of the Earth's shadow is 1.4 million kilometers long, which is three and a half times longer than the distance between the Earth and the Moon. Thus, the Moon lying a few tens of thousands of kilometers farther than normal will not have a significant impact on its travel time.
So this comes down to the combination of:
• being further away, and thus presenting a smaller apparent area across the Earth's shadow,
• being near the apogee, and thus traveling more slowly than at any other time in its orbit, and
• traversing the Earth's shadow along a path of totality very close to the center of the umbra
Although there are absolutely full moons more great as this one over the next century, which will look smaller at that time, and there are certainly more lunar eclipses, and even those that will cross the shadow closer to the center, no will have the combination of all these factors, together, to produce a longer total lunar eclipse
closer to the date, for updates on the livestreams of this event.
Sources: Royal Astronomical Society of Canada | Lunar eclipses of NASA | NASA Goddard Scientific Visualization Studio
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