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Total Lunar Eclipse

Author
by Tanya
Publish date
8 December 2011
Comments
Comments (3)

I don’t know about you, but I’m already feeling the pressure of December madness. Really it’s a fantastic time of the year when we catch up with friends, celebrate with colleagues and generally wind things up for the summer. But cramming all this in alongside final deadlines and the Christmas shopping can be a mighty task!

When it all gets a bit too frantic and crazy, there’s nothing like sitting back and taking in the night sky. And this month, there’s even more reason to do so.

This beautiful composition shows the extent of Earth's shadow. It was taken from Europe, so might recognise that the Moon appears upside down.This beautiful composition shows the extent of the Earth's shadow. It was taken from Europe, so you might notice that the Moon appears upside down.
Source: Laurent Laveder

During the early hours of Sunday 11th December there will be a Total Lunar Eclipse. We can watch the Moon change colour as it plunges into the Earth’s shadow.  

The eclipse begins at 11:46pm (AEDT) on Saturday 10th December as the Sun, Earth and Moon fall into line. At first, the shadow will appear to take a bite out of the Moon. Then, the Moon will enter full shadow or totality, just after 1am on Sunday morning. It will stay in shadow for 51 minutes, a little on the short side for a lunar eclipse as they often continue for over an hour.

By 2am, the Moon will begin to light up again and it’s amazing how bright that first glimpse can be. At 3.17am all will be back to normal.

The interesting thing about an eclipse is that the shadow isn’t completely dark. The Moon takes on a reddish glow as light travels through the Earth’s atmosphere. Depending on conditions, it can also take on a hint of blue around the edges from light that passes through the ozone layer in the Earth’s upper atmosphere.

So what might we see during this eclipse? On NASA’s Science news website, atmospheric scientist Richard Keen of the University of Colarado says:

"I expect this eclipse to be bright orange, or even copper-coloured, with a possible hint of turquoise at the edge."

Sounds lovely, doesn't it? Apparently our atmosphere is nice and clear at the moment. Let's just hope the clouds stay away.

Best to try for this eclipse as we are coming up to some lean years. The next lunar eclipse will be a partial in June 2012. But to see a Total Lunar Eclipse, we'll have to wait until April 2014.

The Moon plunges into the Earth's shadow.The Moon plunges into the Earth's shadow.
Source: Public Domain

Eclipses are uncommon because the Moon's orbit (shown in green) is misaligned with the Earth's orbit around the Sun (shown in blue). If the Moon and Earth orbited in the same plane, we'd see an eclipse every Full Moon (as well as a solar eclipse every New Moon). But because the Moon's orbit is tilted by just 5 degrees, most of the time the Moon misses the Earth's shadow and moves either above or below it.

So enjoy taking some time out to appreciate the Universe we live in, as long as the weather lets us!

 

A treat for early risers

Author
by Tanya
Publish date
16 June 2011
Comments
Comments (1)

A rare event happened this morning... when my one-year-old started calling out for Mummy just after 4am, the usual dread of having to face another cold and early start was gone, replaced by the thrill that my little guy was just the perfect astronomer!

This morning we were treated to a total lunar eclipse and it began with a beautiful starry, but certainly cold, morning sky. Just before 4.30am a small chunk was seen to be missing from the top right of the Moon. The first sign that the Earth's shadow had found its target.

Lunar Eclipse The Earth's shadow hit its target.
Image: Tanya Hill
Source: Museum Victoria
 

Lunar eclipses occur on those rare occasions when the Sun, Earth and Moon are in perfect alignment. They only ever happen at the time of Full Moon, when the Sun and Moon are on opposite sides of the Earth. Most of the time the Earth's shadow misses the Moon, falling either above or below it, but this morning it was right on track.

By 5am, the Earth's shadow was covering more than half the Moon and a reddish glow was already beginning to appear. The stars was twinkling perfectly, with one of my favourite constellations, that of Scorpius, sitting directly to the left of the Moon, and the centre of the Milky Way right above it. Totality officially began at 5.23am and the Moon was certainly an eerie red colour.

Where does that red come from? Well the only way sunlight can now reach the Moon is by passing through the Earth's atmosphere. That light gets bent and scattered, so only the reddest light can make it through. Particles in our atmosphere, like the volcanic ash that's been annoying so many air travellers these last few days, added to the scattering effect, making the eclipse redder and darker than the last few that I remember.

For those who love statistics, totality was due to last 100 minutes, making it the longest lunar eclipse since 2000, which clocked in at 106 minutes. A rough rule of thumb is that totality generally takes around one hour, but a couple of times each decade we get a good one lasting 90 minutes or more. This was one of those.

Except for those pesky clouds that rolled in just after 6am, blocking the view for those who got up at their usual time. They were obviously in need of my own precious little alarm clock.

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