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A Strange Streak Imaged in Australia
Koyaanisqatsi writes "Today's Astronomy Picture of the Day presents a challenge worthy of a large audience: as it says, "Meteor experts don't think it's a meteor. Atmospheric scientists don't think it's lightning". An intriguing dark streak and bright flash that defies explanation showed up on some cloud monitoring pictures. The forumsetup to discuss it is currently hosed, so perhaps fellow slashdotters can shed some light over the mystery?"
but when this pic surfaced the first time, people speculated that the flat trajectory meant it had to be a tiny meteorite, with the flash resulting from the rock hitting a street light. a 1 in a billion photo, I imagine.
"Wow. Now THAT'S a lot of angry Indians." - Lt. Col. George Armstrong Custer
for any sort of natural phenomenon. It suggests a photographic artifact of some sort. Is the flash definitely related? It certainly appears to be coming from the end of what the APoD caption identifies as a light pole, which is not working. Could it have failed with a sudden flash? Could it coincidentally have occurred at the same time as the streak artifact?
Behold the riant ape! Beware, his crooked thumbs!
Except that camera was periodically taking pictures, and the picture right before and the picture right after don't show any problems on the lens.
Weird! I could see the streak until I wiped my screen with a Kleenex and the streak vanished!
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
That was me.
I was trying out my new death-ray. I had it miscalibrated so that you could see it.
Don't worry about it. When death comes and strikes from the heavens for real, it'll be completely invisible.
-Ming the Merciless
Mod me down and I will become more powerful than you can possibly imagine!
There was no alien. The flash of light you saw in the sky was not a UFO. Swamp gas from a weather balloon was trapped in a thermal pocket and reflected the light from Venus.
Nothing to see here, move along folks.
J
Um, film? It was a digital picture to begin with. Check out this in the header of the image:
uExif
Canon
Canon PowerShot G3
ACD Systems Digital Imaging
2004:11:25 15:20:49
0220
0100
2004:11:22 18:52:52
2004:11:22 18:52:52
IMG:PowerShot G3 JPEG
Firmware Version 1.02
OK, here's my solution. The light levels are fairly low: the EXIF data from the big image reveals that the Powershot G3 used 1/20s exposure at f/5.6.
I reckon the streak and the blur are very, very close to the camera, and that the intersection with the streetlamp is conincidence.
I believe that the mystery object is an insect flying "north-west" (i.e. towards the top left of the camera). The EXIF data tells us that the flash was fired, although goodness knows why any decent photographer would use a flash for that shot.
The flash on most cameras fires at the beginning of the exposure time, and the insect is captured in flight and out of focus near the middle of the frame. It then continues flying for the rest of the 1/20s exposure causing the black streak.
Where do I go to collect my prize?
Ydco co
Actually, here is something revealing, it seems that his before and after images are reversed:
$ strings strangebefore_pryde_big.jpg | head
uExif
Canon
Canon PowerShot G3
ACD Systems Digital Imaging
2004:11:25 15:23:11
0220
0100
2004:11:22 18:53:07
2004:11:22 18:53:07
IMG:PowerShot G3 JPEG
$ strings strange_pryde_big.jpg | head
uExif
Canon
Canon PowerShot G3
ACD Systems Digital Imaging
2004:11:25 15:20:49
0220
0100
2004:11:22 18:52:52
2004:11:22 18:52:52
IMG:PowerShot G3 JPEG
$ strings strangeafter_pryde_big.jpg | head
uExif
Canon
Canon PowerShot G3
ACD Systems Digital Imaging
2004:11:25 15:22:47
0220
0100
2004:11:22 18:52:37
2004:11:22 18:52:37
IMG:PowerShot G3 JPEG
$
Canon PowerShot G3
My guess is a very bright event (the failure of the streetlight, probably) causing CCD overexposure and subsequent temporary ill effects on the rest of the CCD scan line. Any Canon geeks in the house who know about the CCD scanning direction of a Powershot G3 and can compare it with the streak "trajectory" angle?
Peter
I've had all sorts of annoying artifacts like this on my image capture setup at home, but generally overloading the CCD produces horizontal and vertical streaks only, which would follow the layout of the CCD (rows and columns?) The image could still be explained by either:
My theory is the bright flash is actually sunlight reflected off the lamp and either overloading the CCD or causing a lens flare just before the image, resulting in this artifact. I get that a lot with cars going by my camera setup at home, especially at sunrise and sunset. The only difference I get is that they're all perfectly horizontal and/or vertical.
Take a look at the way the clouds are moving - I've never seen clouds billowing inwards.
before
"the" picture
after
Paleontologists don't think it is a dinosaur, NASA doesn't think it is a spacecraft, financial experts don't think it will have an adverse effect on the economy, lawyers could be preparing a lawsuit on behalf of Bigfoot for IP infringement, the FDA has said it could have adverse side effect, the White House has declined to comment. Currently the photo is on sale at eBay with the high bid at $785.
My beliefs do not require that you agree with them.
Yes, an ancient, alien artifact, pregnant with long-dormant, world-ravaging evil, which will no doubt unleash terrible plague and death and destruction the world over, consuming the entire human race in an unimaginable apocalypse, only possibly averted by some unlikely everyman hero who has heretofore been overlooked by society but who will, no doubt, be immortalized by his deeds on the day the evil is returned to this artifact and banished forever.
Clear as day. It's right there in the photo.
Nope, CCD blooming happens primarily vertically, sometimes horizontally. Never on an angle. That flash isn't bright enough to cause that massive of an overexposure, and blooming causes the overexposure to bleed into the rest of the column/row, so it would be brighter, not darker. Also, blooming is typically symmetrical from the event, this image has the line going out only in one direction.
Ok, I did some work on this...
First, EXIF fields in the photos... something you should look at first.
Camera: Canon PowerShot G3
Date and Time (original): 2004:11:22 18:52:52
Exposure Time: 1/19 sec.
Aperture: f/5.6
And for the photo After:
Date and Time (original): 2004:11:22 18:52:37
So the photos were taken with 1/19 sec. exposure, every 15 seconds.
I took the two images into GIMP, substracted them, brightened the result a lot (using Levels) and ran it through despecle. First, the lamps do look perfectly identical between the photos (or there'd be a spot around the lamp where it changed shape). In fact, the only bright bits that remain (apart from the sea reflections) are the flash and the streak.
The streak looks conical, at 1-1.5 degrees (I measured roughly using GIMP). It ends before the edge of the picture. It's about 1200 pixels long, in fact. The street lamps are 60 pixels long... Assuming that a street lamp would be on the order of 5-10 metres high, you get about 100-200 metres streak.
The cloud is VERY visible on the difference image; it has yellow-orange central spot and 2 pure-white spots to the sides; this seems consistent with a central fire and a smoke circle.
Now I substracted the before and after image and brightened them the same way. I *think* there is a visible dark spot at the place where the white cloud was; however, the image is so noisy that it could just be my imagination.
I think that the flash and the cloud were from the blown lamp. They dissipated rapidly, but there could be traces left... I'd have to do much better image processing to be able to tell.
I have no idea whatsoever what the dark streak could be. It doesn't look like a CCD sensor problem - overloaded CCDs leak brightness straight up, as far as I know. I also don't know of any lens flare that can darken the photo. It could be smoke, in which case something would be hitting the street lamp. But that would've caused lots of visible damage.
I refuse to use
Actually, additional analysis here shows a slightly more energetic explosion than the original image suggests.
You can see this dark streak almost every day in southern california, or almost anyplace that has contrails visible in the sky. When the contrail goes between you and the sun, you can see a dark band coming down from it. Watch for it!
Basically, what you are seeing is the equivalent of a sunbeam, except that it's a shadow-beam. A sunbeam occurs when there is a small hole in the cloud, and the light going through the hole illuminates the dust particles and water droples in the air along the path of the light. If the light is strong and the background relatively dark, it is easy to see these sunbeams (or God rays.)
Shadows through the sky are somewhat harder to see, because the contrast is not as great. When they are dramatic, as in this picture, you have to have the fortuitous situation of looking through a long, well defined slab of shadowed air, with well-lit air on either side. Airplane contrails are the perfect shadow source for this.
Imagine a 3D volume of a shadow cast by a contrail. It is a long thin slab of shadowed air. If you are within that slab, and looking along it, all the air in that direction is shadowed, for many miles, so the contrast between the shadowed air and the surrounding air is strong.
A good bit of the light around the shadow beam is not light scattered by dust or water droplets, but is just the same Raliegh-scattered light that makes the sky blue. The dark streak through the sky will be noticably darker and especially less blue than the surrounding air.
As you can tell, this is one of my favorite (of many!) atmospheric optical phenomena. Once you start to look for them, they are quite easy to see. Occasionally you can see them from natual cloud formations or even topographical or architechural features when the conditions are just right.
Thad Beier
I love Mondays. On a Monday, anything is possible.
Maybe this will shed some light. It's a Photoshop "difference" between the before image and the mystery image, with a bit of levels adjustment to make it more obvious. http://img119.exs.cx/my.php?loc=img119&image=x2fst rangeprydebigdi.jpg
I think that one came from the George Lucas expanded edition of the original.
the streak "trajectory" angle
The streak angle, BTW, is exactly arctan(2/3) -- the streak goes two pixels up for every three across. (It goes 652 pixels up and 978 across, which is less than 1% different from 2/3, smaller than the error of me pointing at things in the Gimp.) To me this makes it very likely to be an artifact.
Peter