APOD: A Sun Halo Beyond Stockholm (2011 Jan 10)

[APOD Robot]

A Sun Halo Beyond Stockholm

Explanation: What's happened to the Sun? Sometimes it looks like the Sun is being viewed through a large lens. In the above case, however, there are actually millions of lenses: ice crystals. As water freezes in the upper atmosphere, small, flat, six-sided, ice crystals might be formed. As these crystals flutter to the ground, much time is spent with their faces flat, parallel to the ground. An observer may pass through the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for sundogs. The above image was taken last year in Stockholm, Sweden. Visible in the image center is the Sun, while two bright sundogs glow prominently from both the left and the right. Also visible is the bright 22 degree halo -- as well as the rarer and much fainter 46 degree halo -- also created by sunlight reflecting off of atmospheric ice crystals.

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[webolife]

This picture also shows the circumhorizontal halo, produced by the same effects as the sundogs, as well as the pillar of fire produced by columnar ice crystals tumbling down parallel to the horizon.

[owlice]

I don't see a circumhorizontal arc in that image; where are you seeing it?

[metleif]

The halo as well as the sun pillar appears to be in front of the distant landscape, so it’s a low level phenomenon: diamond dust, formed in moist and very cold air close to the ground. It's very low cirrus clouds...

[royalpalms6]

When are we going to see photos of SPACE?

[orin stepanek]

Thanks for sharing Peter; I love the photo.

[Indigo_Sunrise]

When are we going to see photos of SPACE?

Come back tomorrow.......

[bystander]

When are we going to see photos of SPACE?

Come back tomorrow.......

But there won't be anything to complain about, then.

[Indigo_Sunrise]

When are we going to see photos of SPACE?

Come back tomorrow.......

But there won't be anything to complain about, then.

Right, my mistake.

[Hofi]

If you look closely, you can even find another ring outside the main ring.
It lies about twice the radius of the main ring and is especially visible on
the horizon.

If you cannot see the second ring, try to watch your screen from another angle than
usually. (f.i. from the side). Then, the ring comes out more clearly...

[neufer]

<<The Stockholm Observatory is an astronomical institution in Stockholm, Sweden, founded in the 18th century and today part of Stockholm University. The first observatory was established by the Royal Swedish Academy of Sciences was begun in 1748, and the building was completed in 1753. It is situated on a hill in a park nowadays named Observatorielunden.

Adriaan van Maanen (left) & Bertil Lindblad (center)
on the platform for observation at the
Newton focus of the 1 meter reflector of the
Stockholm Observatory in Saltsjöbaden 1938.

Bertil Lindblad (Örebro, 26 November 1895 – Saltsjöbaden, 25 June 1965) was professor and astronomer of the Royal Swedish Academy of Sciences and head of the Stockholm Observatory from 1927 to 1965. Lindblad was responsible for the observatory's move from the old building in the centre of Stockholm to a newly built facility outside of Stockholm in Saltsjöbaden (Salt bath) in 1931.

Lindblad studied the theory of the rotation of galaxies. By making careful observations of the apparent motions of stars, he was able study the rotation of the Galaxy. He deduced that the rate of rotation of the stars in the outer part of the galaxy, where the Sun is located, decreased with distance from the galactic core. A certain class of resonances in rotating stellar or gaseous disks are named Lindblad resonances, after Bertil Lindblad.

A Lindblad resonance is an orbital resonance in which an object's epicyclic frequency is a simple multiple of some forcing frequency. Resonances of this kind tend to increase the object's orbital eccentricity and to cause its longitude of periapse to line up in phase with the forcing. Lindblad resonances drive spiral density waves both in galaxies and in Saturn's rings.

Lindblad resonances affect stars at such distances from a disc galaxy's centre where the natural frequency of the radial component of a star's orbital velocity is close to the frequency of the gravitational potential maxima encountered during its course through the spiral arms. If a star's orbital speed around the galactic centre is greater than that of the part of the spiral arm through which it is passing, then an inner Lindblad resonance occurs - if smaller, then an outer Lindblad resonance. At an inner resonance, a star's orbital speed is increased, moving the star outwards, and decreased for an outer resonance causing inward movement>>

[bystander]

If you look closely, you can even find another ring outside the main ring.
It lies about twice the radius of the main ring and is especially visible on
the horizon.

If you cannot see the second ring, try to watch your screen from another angle than
usually. (f.i. from the side). Then, the ring comes out more clearly...

Also visible is the bright 22 degree halo -- as well as the rarer and much fainter 46 degree halo

[owlice]

When are we going to see photos of SPACE?

Right now if you'd like, just by going here, where you can see recent submissions to APOD. Then later, should one of them become an APOD, you can complain that you've already seen it!

[Manu61]

This photo looks like featuring a much more rare phenomenon: the 44° parhelia (actually secondary 22° sundogs from very bright sundogs).
There is also a hint of something tangent at the 22° halo top.

[neufer]

http://www.ursa.fi/blogit/ice_crystal_h ... p?m=200802
http://www.ian.cz/redsys/upload/631-380.jpg

This photo looks like featuring a much more rare phenomenon: the 44° parhelia (actually secondary 22° sundogs from very bright sundogs).

There is also a hint of something tangent at the 22° halo top.

http://vjac.free.fr/skyshows/icehalos/icehalos.html

<<An upper tangent arc is a halo, an atmospheric optical phenomenon which appears over and tangent to the 22° halo around the sun.

The shape of an upper tangent arc varies with the elevation of the sun; while the sun is low (less than 29–32°) it appears as an arc over the sun forming a sharp angle. As the sun rises, the curved wings of the arc lower towards the 22° halo while gradually becoming longer. As the sun rises over 29–32°, the upper tangent arc unites with the lower tangent arc to form the circumscribed halo.

Both the upper and lower tangent arc form when hexagonal rod-shaped ice crystals in cirrus clouds have their long axis oriented horizontally, while otherwise rotated in any direction. This orientation of the crystals also produces other halos, including 22° halos and sun dogs, but a predominant horizontal orientation is required to produce a crisp upper tangent arc. Like many other halos, upper tangent arcs grade from a red inner edge to a blue outer edge because red light is refracted more strongly than blue light.

[skippy]

Another waste of SPACE--get it? Waste of Space?

NOW

Here is something FAR more astronomical
http://www.liveleak.com/view?i=9d9_1294631331

[owlice]

http://asterisk.apod.com/vie ... 29&t=22549

[Céline Richard]

If i have been in Stockholm, at the time of this phenomenon, i wonder how i would have felt. I think i would have been so surprised, even rather afraid...
When we don't understand something, we seek answers. I could have thought to a science-fiction "explanation" (ex: another universe opens between the Earth and the Sun! Or, what happens to the magnetosphere, has the polarization of the magnetosphere changed, so it quites Poles, an aurora is happening in broad daylight! What will be the effect of solar wind on human health?).
I prefer to know the origins of the phenomenon lies in water vapor inside the atmosphere
As the Sun is near the horizon line, it travels through a deeper "screen" of atmosphere, but i have never seen this.
A very impressing picture!

Céline

[wwcsig]

It's a stunning and beautiful picture, no doubt. But shouldn't the fact that this is obviously a composite of at least two pictures with different exposure settings be mentioned? A shot right into the sun that has even the shadows on the sides of the buildings correctly exposed is hardly possible. Doesn't the combination of the multiple images distort the actual halo it is depicting?

[Céline Richard]

It's a stunning and beautiful picture, no doubt. But shouldn't the fact that this is obviously a composite of at least two pictures with different exposure settings be mentioned? A shot right into the sun that has even the shadows on the sides of the buildings correctly exposed is hardly possible. Doesn't the combination of the multiple images distort the actual halo it is depicting?

You say this picture could be a hydride of two, with different exposure? I thought i could see this in the sky for real! Actually, i have been looking for the shadows on the sides of the buildings correctly exposed, but i don't find it.

Have a very nice day

Céline

[Chris Peterson]

You say this picture could be a hydride of two, with different exposure? I thought i could see this in the sky for real!

You can see exactly this with your own eyes when the conditions are right, and it will look very similar to what the image shows.

Some people get very upset at the idea of composite digital images. But the reality is, our eyes have orders of magnitude wider dynamic range than the best cameras. You can stand in sunlight and clearly see detail in both the brightest and the most shadowed areas- something that no camera can do. (In reality, there is more than your eyes involved here- your brain actually builds up an image as your eyes move around. Yes! What you see with your own eyes is also a composite, both of exposure and a mosaic.)

It is possible to make an image that comes closer to visual reality by taking several exposures and combining them cleverly. Tools for doing this are routinely available in image processing software, and some cameras now take two or more images in quick succession and silently combine them into a single image before you ever see it.

I don't know if this image is such a composite, but I do know that this type of shot usually produces a more realistic image when composited from multiple exposures, and I also know that the image quite accurately represents the true visual appearance of a halo display.

[Céline Richard]

You can see exactly this with your own eyes when the conditions are right, and it will look very similar to what the image shows.

Such a good news! I hope i will have the opportunity to see a halo like that one day!
Do you know if there are places on Earth, where we would be more likely to admire a halo, compared with other places?

Some people get very upset at the idea of composite digital images. But the reality is, our eyes have orders of magnitude wider dynamic range than the best cameras.You can stand in sunlight and clearly see detail in both the brightest and the most shadowed areas- something that no camera can do. (In reality, there is more than your eyes involved here- your brain actually builds up an image as your eyes move around. Yes! What you see with your own eyes is also a composite, both of exposure and a mosaic.)

I didn't know what we see is a composite, this is very interesting. I hope researchers will be able to make artificial eyes, which would enable blind people to recover the vision, then to see as well as people with biological eyes, soon. Some researchers have already made artificial eyes, by connecting the eye to the brains, so indeed, it is linked to the brains... so it might be very complicated.

It is possible to make an image that comes closer to visual reality by taking several exposures and combining them cleverly. Tools for doing this are routinely available in image processing software, and some cameras now take two or more images in quick succession and silently combine them into a single image before you ever see it.

Yes, my camera can do that by night! If i can put my camera on the ground, or on a wall, a table, etc. the images are very beautiful. Unfortunately, if i take pictures while taking my camera with my hands, the images are blurred, even if i try not to move at all. When light is week, at night, is light, the longer it is to take a picture, the harder it results not to move at all.

I don't know if this image is such a composite, but I do know that this type of shot usually produces a more realistic image when composited from multiple exposures, and I also know that the image quite accurately represents the true visual appearance of a halo display.

Thank you a lot

Céline

PS: picture 1 from http://www.boingboing.net/200811120918.jpg
picture 2 from http://www.doctissimo.fr/html/sante/mag ... ficiel.htm

[Chris Peterson]

Do you know if there are places on Earth, where we would be more likely to admire a halo, compared with other places?

The best halo displays involve lots of ice crystals in the air. It's no coincidence that so many of these excellent halo images are taken from polar or near polar locations.

RESISTANCE IS FUTILE!

[Céline Richard]

The best halo displays involve lots of ice crystals in the air. It's no coincidence that so many of these excellent halo images are taken from polar or near polar locations.!

Thank you Chris

Any machine connected to brains is a little bit worrying, indeed, but this is against blindness: the man becomes free then, as he can go wherever he would like to, alone, without anyone to guide him. If i was blind, i think i would like to have one, don't you?

Have a very nice day!

Céline

[PeterR]

Hello everyone,
I am the author of this picture and I just discovered that there was a discussion going on so I am jumping in, a little bit late maybee.
First of all let me tell you that it was a truely magical display that I have never had the oportunity to wittness before. The light was blinding and iridescent at the same time and it went on untill sunset varying in intesity and the display of various arcs became more or less apparent as conditions changed over time.
This is not a composite of 2 pictures but of no less than 64!
8 overlapping pictures for a 360° panorama and each of them exposed with 8 different shuttertimes to register the huge contrast from the brightest highlights in the sundogs to the deepest shadows in the buildings. This picture is a crop of approximately 150°.
I then worked for more than a full day trying to reproduce the visual impression just like you so well described it Chris - thank you.
I did not use any HDR-software but painted in different parts in Photoshop to get it just the way I wanted. Does that make it only an artistic interpretation? I don't think so as I have only tried to balance details present in the originals.
I could have taken a single shot as you suggest, wwcsig, but then I doubt that my picture would have been selected for an APOD and you would never have seen it.
And yes, I think there is a 44° parhelia just inside the 46° halo.

There is a famous painting called "Vädersoltavlan" depicting an intricate halo over Stockholm in 1535. It is also the oldest known representation of Stockholm.
My photograph is not from the same spot and not exactly in the same direction but otherwise I think it may be an interesting parallel: http://en.wikipedia.org/wiki/Vädersolstavlan and http://www.atoptics.co.uk/fz346.htm

/*Peter Rosén