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Eclipse chasers flock to the Pilbara

Updated Fri May 10, 2013 4:23pm AEST
Annular eclipse 100513 Photo: "Ring of fire" - the complete annular eclipse of the sun captured shortly after sunrise south of Newman. (Supplied: Rob Whitehead)
Map: Karratha 6714

This morning's annular eclipse saw photographers join eclipse chasers and documentary makers from around the world in WA's Pilbara, all eager to catch a glimpse, and the perfect shot, as the moon passed across the sun.

On the eclipse's central line, south of Newman in the Pilbara, the moon covered most of the sun.

Astronomical Officer Greg Lowe says the eclipse is named for its shape.

"This one is called an annular eclipse because the sun appears as a thin ring all the way around the moon and a thing ring as in I guess a wedding ring is also called an annulus if you're doing geometry, like a skinny donut," he said.

"If you are right on the eclipse path then the moon will be centrally located right in line with the sun, but the sun will appear as a bright ring all the way around the moon."

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Annular eclipse near Newman (3) Photo: Eclipse as the moon moves away, using a solar filter to show sun surface detail, including sunspots. (Supplied: Rob Whitehead)

Across the rest of WA there was a partial eclipse.

Pilbara based landscape photographer Rob Whitehead says preparations to catch the perfect shot began well before dawn, driving through the dark to find the perfect spot.

"We drove approximately 100 kilometres south of Newman before turning up the Jigalong Mission Road and continuing on to a high vantage point with an unobstructed view," he said.

"The annularity began about 10 minutes later (after dawn)," he said.

"This lasted three and a half to four minutes, however, as the sun and moon slowly diverged paths, a partial eclipse was present for more than an hour."

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Annular eclipse Photo: A ring of fire caused by an annular eclipse of the sun south of Newman, on May 10, 2013. (Supplied: Rob Whitehead)

Mr Lowe says there will be a long wait for the next solar eclipse.

"It's a bit of a wait now, the next you can look forward to and this will be a total eclipse, is in April of 2023," he said.

The best vantage point for the next one is expected to be in Exmouth.

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Photo: The annular eclipse captured from Jigalong Mission Road, south of Newman. (Supplied: Rob Whitehead)
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Wolfram|Alpha have a suite of astronomy tools that can be accessed for free from their website
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On July 22 2009 the longest and brightest solar eclipse of the 21st century lasted for 6 minutes, 39 seconds. The shadow from the eclipse was only visible on the ground in certain regions across the Pacific and Indian oceans for a very brief period of time.

A mathematician from the Czech Republic and some of his colleagues were able to capture and composite 31 photographs from that day's events. The wispy lines visible around the moon are actually the sun’s corona.

Another solar eclipse of that magnitude is not expected until 2132.

More info: bit.ly/136gUil

Photo credit: Miloslav Druckmüller, Peter Aniol, Vojtech Rušin, Ĺubomír Klocok, Karel Martišek, Martin Dietzel
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PDF document detailing discovery
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The Tunguska impact event is one of the great mysteries of modern history. The basic facts are well known. On 30 June 1908, a vast and powerful explosion engulfed an isolated region of Siberia near the Podkamennaya Tunguska River.

The blast was 1000 times more powerful than the bomb dropped on Hiroshima, registered 5 on the Richter scale and is thought to have knocked down some 80 million trees over an area of 2000 square kilometres. The region is so isolated, however, that historians recorded only one death and just handful of eyewitness reports from nearby.

But the most mysterious aspect of this explosion is that it left no crater and scientists have long argued over what could have caused it.

The generally accepted theory is that the explosion was the result of a meteorite or comet exploding in the Earth’s atmosphere. That could have caused an explosion of this magnitude without leaving a crater. Such an event would almost certainly have showered the region in fragments of the parent body but no convincing evidence has ever emerged.

In the 1930s, an expedition to the region led by the Russian mineralogist Leonid Kulik returned with a sample of melted glassy rock containing bubbles. Kulik considered this evidence of an impact event. But the sample was somehow lost and has never undergone modern analysis. As such, there is no current evidence of an impact in the form of meteorites.

That changes today with the extraordinary announcement by Andrei Zlobin from the Russian Academy of Sciences that he has found three rocks from the Tunguska region with the telltale characteristics of meteorites. If he is right, these rocks could finally help solve once and for all what kind of object struck Earth all those years ago.

Zlobin’s story is remarkable in a number of ways. The area of greatest interest for meteor scientists is called the Suslov depression, which lies directly beneath the location of the air blast and is the place where meteorite debris was most likely to fall.

Dig into the peat bogs here and you can easily find layers that show clear evidence of the explosion. Zlobin said he dug more than ten prospect holes in the hope of finding meteorite fragments, but without success.

However, he had more luck exploring the bed of the local Khushmo River, where stones are likely to collect over a long period of time. He collected around 100 interesting specimens and returned to Moscow with them.

This expedition took place in 1988 and for some unexplained reason, Zlobin waited 20 years to examine his haul in detail. But in 2008, he sorted the collection and found three stones with clear evidence of melting and regmalypts, thumblike impressions found on the surface of meteorites which are caused by ablation as the hot rock falls through the atmosphere at high speed.

Zlobin and others have used tree ring evidence to estimate the temperatures that the blast created on the ground and says that these were not high enough to melt rocks on the surface. However, the fireball in the Earth’s atmosphere would have been hot enough for this.

So Zlobin concludes that the rocks must be fragments of whatever body collided with Earth that day.

Zlobin has not yet carried out a detailed chemical analysis of the rocks that would reveal their chemical and isotopic composition. So the world will have to wait for this to get a better idea of the nature of the body.

However, the stony fragments do not rule out a comet since the nucleus could easily contain rock fragments, says Zlobin. Indeed he has calculated that the density of the impactor must have been about 0.6 grams per cubic centimetre, which is about the same as nucleus of Halley’s comet. Zlobin says that together the evidence seems “excellent confirmation of cometary origin of the Tunguska impact.”

Clearly there is more work to be done here, particularly the chemical analysis perhaps with international cooperation and corroboration.

Then there is also the puzzle of why Zlobin has waited so long to analyse his samples. It’s not hard to imagine that the political changes that engulfed the Soviet Union in the year after his expedition may have played a role in this, but it still requires some explaining.

Nevertheless, this has the potential to help clear up one of the outstanding mysteries of the 20th century and finally determine the origin of the largest Earth impact in recorded history.

Ref: arxiv.org/abs/1304.8070: Discovery of Probably Tunguska Meteorites at the Bottom of Khushmo River’s Shoal

Originally posted on technology review
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Pretty darn amazing what the sensors that are stationed all over the world detect.
Now if we could just detect this stuff at a range that was far enough away from the planet to be able to do something about it instead of after the fact when the damage has already been done...


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