Here is how Friday is superlong lunar eclipse works



Longest lunar eclipse of the century: What you should know

An overview of what you need to know about the longest lunar eclipse of the century, the ‘blood moon’ eclipse, and why do you have to travel to see it.

Have you ever noticed that if there is a solar or lunar eclipse, an eclipse of another sort is two weeks before or after? Sometimes, we even get three eclipses in less than a month.

Such a situation is currently happening. We already have a partial eclipse of the sun this month, on Friday the 13th, are visible only from parts of Antarctica, Tasmania, Australia and a very small part of New Zealand. Another partial solar eclipse will take place on Aug. 11; it will be visible for those in northern Europe and a large part of central and eastern Asia. Even parts of the far north and the east of Canada gets a look in the kitchen at sunrise.

And right in the middle, between the two eclipses, there will be a total eclipse of the moon on 27 July. [Blood Moon 2018: Longest Total lunar eclipse of the Century Occurs July 27]

That is because on that day, the moon will cross the ecliptic, the line that marks the sun’s path around the sky. If the moon crosses the ecliptic when it is full, we get an eclipse of the moon, as the moon crosses the ecliptic when it is new, we get an eclipse of the sun. Incidentally, this is the reason that the sun’s path around the sky called the “ecliptic” for the “eclipse”!

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  • Mars in opposition

And every time there is a full moon or new moon crosses the ecliptic on one side of the lunar orbit, it will also be on the line on the other side of the moon, two weeks earlier or two weeks later. We call this period an “eclipse season.”

Three for the price of two

We usually get two eclipses during a solar eclipse season. But, as just noted, during this current eclipse season, not two, but three eclipses will take place within a single synodic month of 29.53 days — the length of time it takes to get from one new moon to the next.

The next total eclipse of the moon on the 27th of July is especially noteworthy, because the satellite will pass just north of the center of the Earth in the shade. In fact, the moon will reach the descending node of its orbit — the point at which it crosses the ecliptic going from north to south — only 138 minutes after arrival at the full phase, resulting in an almost central total eclipse.

Because of this, the two new moons, which are on the sides of the 27 July full moon skirt just close enough to the moon compared to the (ascending) node of the moon to a marginal eclipse of the sun. So, we have three eclipses instead of the usual two.



A small, slow moon + a big shadow = a long eclipse

Another artifact of the moon in the vicinity of a central passage of the Earth a shadow is that totality lasts an unusually long time. Actually, the moon’s path through the shadow is only one factor in making a long-term total phase; the moon’s distance has also an effect. About 14 hours before it is full, and the moon will be at its farthest point from Earth (apogee), a distance of 252,415 km (406,223 km), and the moon moves slowest on the track when he is farthest from the Earth.

This also results in a full moon is much smaller than the average; in fact, this is the smallest full moon of 2018. This solar eclipse will take place three weeks after the Earth arrived at aphelion, the farthest point in the orbit of the planet from the sun, when the Earth threshold shadow appears largest in angular size.

So, counting it all, we have a small moon, moves slower than normal, it goes almost right through the middle of a larger-than-normal shadow of the Earth. This will result in an unusually long solar eclipse, the total phase lasts 1 hour and 43 minutes, just 4 minutes shy of the longest possible totality. According to the “Five Millennium Canon of lunar eclipses: (-1999to +3000)” by Fred Espenak and Jean Meeus, this is the longest total lunar eclipse the Earth will see up to and including June 9, 2123.

The average duration of a total lunar eclipse is about 50 minutes.

North America closed

Now for the bad news, if you live in North or Central America: None of this eclipse will be visible in these places — not even the partial phases, because the entire event will take place in the course of the midday and afternoon hours, when it will be daytime and the moon is below the horizon.

However, if you happen to be in Europe, Africa or Asia, you will be able to see the event. The moon appears directly overhead of a point on a few hundred miles off the east coast of Madagascar in the Indian Ocean.

Much of Japan and eastern Australia will see the moon, while in total eclipse. The central and eastern parts of South America to see the moon during or after the totality.

Do not forget Mars

Together with the fully eclipsed moon, something else in the sky will vie for the attention of: Mars. On the day of the eclipse, Mars is in opposition with the sun. Shines with a brilliant yellow-orange glow, this planet will be located about a half-dozen degrees below the moon. Some old eclipse fans may recall a similar coupling of a totally eclipsed moon with Mars in an exceptionally clear opposition in the Aug. 6, 1971. That eclipse, as this upcoming, was only visible from the Old World.

Until next time…

The next total eclipse of the moon will occur Sunday, Jan. 20, 2019.

If to try to compensate for North Americans who will miss out on this summer, the show, the next lunar eclipse will be a strong supporter of the Western Hemisphere. Of the most of the United States and Canada, the eclipse will be visible from start to finish, with all occurring during the convenient “prime-time” in the evening hours. In addition, the totally eclipsed moon will appear very high in the winter sky.

It will also occur during the three days of Martin Luther King Jr. holiday weekend, to ensure a large viewership on a national level. This will be the first time that a total lunar eclipse occurred during a holiday weekend since May 1975. In short, it will probably be a very popular and long-awaited celestial event.

Hopefully the weather in your area will work. Mark your calendar.

Editor’s note: If you snap a great photo of Friday, the total lunar eclipse and would like to share it with for a story or photo gallery, comments and images

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