The Eye of Sauron Appears Over Sweden

Bad Astronomy
The entire universe in blog form
April 27 2014 7:30 AM

The Eye of Sauron Appears Over Sweden

© Fotograf Göran Strand
Sometimes when you stare into the abyss ...

Photo by Göran Strand, used by permission

It’s a little bit weird to think that sometimes, when you look at the sky, it looks like it’s looking back.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

That shot was taken by astrophotographer (and friend of the BA blog) Göran Strand. It shows an amazing display of atmospheric optics caused by ice crystals high in the atmosphere. He took it on April 25, 2014, around noon local time.

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There are three main optical phenomena seem here. The circle around the Sun is the 22° halo, which is relatively common. It’s formed when ice crystals (likely shaped like hexagonal cylinders) bend light around the Sun. It sometimes can have a red inner edge, which you can see faintly in Strand’s original shot.

Below it and to the left is part of the much more rare 46° halo. The rainbow colors are a bit more obvious, and if you look to the right, just over the trees and underneath the squiggly contrail, you can see another part of the halo.

Update, April 27, 2014 at 17:30 UTC: I originally wrote that the upper arc is the Parry arc, a rare phenomenon. However, commenter exscape pointed out the upper arc is more likely to be an upper tangent arc, and I agree. I have updated the post below to reflect this.

But the kicker here is the wide arc over the 22° halo, just touching it at the top. I originally thought it was the Parry arc, but now I am more inclined to think it's an upper tangent arc, which is similar but more common. As the Sun rises the upper arc changes shape; it has a gull-wing shape at first, but as the Sun rises it drops a bit, becomes more of a single arc, and then appears to "rest" on top of the 22° halo. Not only that, but a lower arc appears below the halo, and that would explain the brightening you can see there as well. Eventually, as the Sun gets high enough, the two tangent arcs turn into a circumscribed halo, completely circling the Sun. It looks to me that Strand caught this in the process of occurring.

That, plus the Sun right in the middle, really makes this look like an eye. I imagine that before we had an understanding of modern science and optics, stuff like this must’ve freaked the hell out of people. Even with our fancy schmancy science now, it still looks a little bit distressing.

But also beautiful and spectacular! I would love to see a really brilliant display like this. These optical phenomenon are truly amazing to see in the sky with your own eyes. I’ve seen dozens of 22° halos, and even a few of the rarer displays too, and it never ever gets old. Beauty never does.

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