total-supermoon-lunar-eclipse

Total Supermoon Lunar Eclipse

The Supermoon Total Lunar Eclipse Explained:

When is the Next Total Supermoon Lunar Eclipse?

The next Supermoon lunar eclipse will take place on September 27, 2015 for the first time since 1982, and according to NASA, for the last time until 2033. The total lunar eclipse, which astronomers describe as a rare event, will be visible to observers in both North and South America, Europe, Africa, the western parts of Asia, and the Eastern Pacific Ocean region.

The exact time of the commencement of this spectacular astronomical event varies, and is dependent on the location of the observer, but totality, which is when the entire disc of the Moon is in Earth’s shadow, is expected to last for only a few minutes, so do not forget to mark this date, September 27, 2015 on your calendar!

For reference, the eclipse’s shadow will start showing at 8:11 p.m. EDT, the total eclipse starts at 10:11 p.m. EDT and peaks at 10:47 p.m. EDT. Use this handy time zone converter to calculate the start and end times of this Supermoon total lunar eclipse for your location.

What is a Supermoon Exactly?

So what makes this total supermoon lunar eclipse (properly referred to as the perigee-syzygy of the Sun-Earth-Moon system) different from  a “normal” total lunar eclipse? You may well ask, so let us look at some of the basic astronomical principles involved when eclipses occur.

 

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“Photograph of the Supermoon at Umaid Bhavan Palace, Jodhpur” by Gk1089 – Photograph captured by me from a point near Circuit House, Jodhpur.Previously published: http://i.imgur.com/eHXgKf7.jpg. Licensed under CC BY-SA 3.0 via Commons – https://goo.gl/JExZ2a

 

Supermoon explained.

The term “supermoon” is not an astronomical term at all, but it derives from astrology, and more specifically from a definition provided in 1979 by astrologer Richard Nolle, when he said that a supermoon occurs when

“…a new or full moon [which] occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). In short, Earth, Moon and Sun are all in a line, with Moon in its nearest approach to Earth.”

In layman’s terms, there is not much to add to this, except to say that when the Moon is full at its closest approach to Earth (perigee), the apparent size of the Moon’s disc is up to 14% larger, and 30% brighter as compared to its size and brightness during apogee, which is when the Moon is at its furthest point from earth in its orbit.

The Moon’s Orbit and Eclipses Explained.

The Moon’s orbit is the result of a complex set of factors and gravitational influences, and particularly from the Sun, but for our purposes, we will focus on just a few basic features of our satellites’ orbit, such as the facts that:

  • it does not orbit the Earth around Earth’s equator
  • it orbits the Earth in an elliptical orbit
  • the Moon’s orbit is inclined with respect to Earths’ orbit around the Sun by slightly more than five degrees

The first point is important simply because an observer’s position on the globe relative to the equator determines the position in the sky (relative to other objects), in which the observer sees the Moon. Of course, there is slightly more to it than that, but suffice to say that the Moon can be visible in some parts of the world when it is not in other parts.

 

moon-orbit

“Lunar libration with phase2” by Tomruen – English Wikipedia, original upload 7 September 2005 by Tomruen [1]. Licensed under Public Domain via Commons – https://goo.gl/Yj3nRX

Point number two is important with regard to the size of the Moon’s disc as seen from Earth during different times of the year. The Moon has an average distance of 239,000 miles (384 600 km), but the long axis of the ellipse that forms the Moon’s orbit has a length of 252,000 miles (405,600 km), while the short axis has a length of only 226,000 miles (363,700 km).

This means that the distance between apogee (the furthest remove), and perigee (the closest approach,) of the Moon is 13,000 miles (20,900 km). This difference is significant, and sufficient to make the Moon appear larger or smaller when seen from Earth, depending on where the Moon is in its orbit.

Lunar eclipses explained.

Of the three points listed above, point number three is the most important with regard to how an eclipse happens, and why a total lunar eclipse is not always visible from all points on the globe when it does happen.

Picture this, as the Earth orbits the Sun, the planet casts a permanent, cone-shaped shadow into space, much like a watch tower shines a beam of light into the atmosphere as it rotates.

However, as the Earth orbits the Sun, the Moon orbits Earth once every 27 days or so, and because of this it is inevitable that at some point, Earth will be between the Sun and the Moon.

 

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“Geometry of a Lunar Eclipse” by Sagredo – Own work, images of Earth and Moon derived from NASA images. Licensed under Public Domain via Commons – https://goo.gl/xpnZiu

 

If the Moon orbited Earth along its equatorial plane, we would see a total lunar eclipse every time the Moon passed through the permanent shadow cast by Earth.

However, we do not see this happen and the reason is that the Moon orbits Earth in a plane that is inclined relative to both Earth’s equatorial plane, and the ecliptic (the path the Earth follows around the Sun).

There are other angles and inclinations involved as well, but the two mentioned here cause the Moon to sometimes pass below and at other times to pass above Earth’s shadow.

Occasionally though, the Moon just grazes Earth’s shadow, an occurrence that is known as a partial eclipse. Where in the world this event is visible depends mainly on the observer’s position on the globe. So why is the upcoming supermoon lunar eclipse such a big deal?

Total Supermoon Lunar Eclipse Explained.

This is a rare event and on happens every few decades. Imagine the Moon being full, the Moon being at perigee (closest to Earth), a lunar eclipse taking place and all at the same time. If all 3 of these happen, you get all the ingredients needed for a Total Supermoon Lunar Eclipse!

On September 27,2015 the Moon will be at a point in its inclined orbit that will allow it to pass through the Earth’s shadow somewhere near the center of Earth’s shadow.

 

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Photo by Stephen Mudge, https://flic.kr/p/oGek3v

 

This is how the total lunar eclipse will be visible and from such a large area on Earth’s surface. Keep in mind, the start and end times of the total lunar eclipse will differ depending on the location of the observer.

Why Will Times Vary?

The Earth’s rotation does not affect the shape of its cone-shaped shadow, but as the planet rotates observers turn into the shadow as night falls, which is why some observers will see it earlier than others.

The Moon will be completely covered by Earth’s shadow at around 11:11 pm ET, during which time the Moon will take on a red, coppery hue, hence the term “Blood Moon”.

 

total-supermoon-lunar-eclipse-red-hue

Photo by Bo Insogna, TheLightningMan.com, https://flic.kr/p/oqiH8C

 

Since some sunlight will still fall on the Moon due to the mass of the Earth slightly bending the light from the Sun as it passes Earth.

 

blood-moon-eclipse

Photo by Christian Ronnel, https://flic.kr/p/nkTf6C

 

If the Earth didn’t bend some of the sunlight during a total lunar eclipse, the Moon would disappear during the time it was in Earth’s shadow. The only way we’d know it was still there would be because the ocean tides would continue in motion.

Did you know?

The Moon does not have a dark side. During times when the Sun does not illuminate the Moon, the pale appearance of the Moon still observable is because it’s partially illuminated by sunlight that reflects off Earth.

When this happens, the side of the Moon that is looking away from the Earth is fully illuminated by the Sun.

 

 

Featured image by “Supermoon comparison” by Marcoaliaslama – Own work. Licensed under CC BY-SA 3.0 via Commons – https://goo.gl/CuOxY7
Sources:
http://www.space.com/30427-supermoon-total-lunar-eclipse-september-video.html
https://en.wikipedia.org/wiki/Supermoon
https://en.wikipedia.org/wiki/Lunar_eclipse
http://www.moonconnection.com/apogee_perigee.phtml
http://www.timeanddate.com/eclipse/total-lunar-eclipse.html

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