Look! Up in the sky! It’s…it’s… it’s an amazing optics display

By Phil Plait | November 1, 2012 7:00 am

It’s funny what tiny little ice crystals can do. Floating high in the air, suspended by air currents, they hang there… and then a ray of sunshine enters them. The light gets bent due to complicated physics, the interplay of that beam of light passing from air to a solid crystal and out again. But once that beam leaves, the sky can light up with a wizard’s pattern of colors and shapes. And if you’re very, very lucky, you’ll see something that you’ll remember the rest of your life.

Something like this:

Holy diffractionation! [Click to heliocanesenate.]

Mind you, this picture is real. David Hathaway – appropriately enough, a solar physicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama – took it using a wide-angle lens to get the whole thing. It’s a High Dynamic Range shot, meaning he combined pictures with 3 different exposure times to see both faint and bright things simultaneously. He took the shot on October 30, 2012.

Everything you’re seeing here is pretty well understood: they all have a name and a specific set of circumstances under which you can see them.

The Sun is the bright blob near the horizon. It’s circled by the 22° halo, a fairly common optical effect in the winter; I see dozens every season. On either side of the Sun are parhelia, nicknamed sundogs. Those are the teardrop-shaped rainbows. Sometimes, as seen here, these stretch out into long streamers called parhelic circles. They are parallel to the horizon but in this wide-angle shot the shape is distorted, bending them up.

Directly above the Sun, dipping down to touch the halo (the math term for this is osculating, which means kissing) is a gull-wing curve called the tangent arc. Above it, connecting the "wings", is the Parry arc.

As an aside, I’ve seen tangent arcs only twice in my entire life. One was at a University of Virginia football game in the winter when the Sun was setting. It was so bright and looked so much like a V that I joked that it was a sign we’d win the game. Georgia Tech trounced us. So much for divination using signs in the sky.

Above the tangent and Parry arcs is a faint rainbow (well, it’s not caused by raindrops, but it’s broken up into colors and has the familiar rainbow-shape) called the Parry supralateral. Faint and off to the right, nicking the supralateral, is a tightly-curved rainbow called the Parry infralateral.

Amazingly, there are still two more to go! The upside-down rainbow at the top is called a circumzenithal arc, because it’s centered on the zenith, the point directly above your head.

Finally, the last thing I can see is a very faint white vertical oval on either side of the the 22° halo and going off the top of the frame, past the circumzenithal arc. That’s the heliac arc, something I’d never even heard of before looking it up here. That’s a new one for me.

Amazing, aren’t they? And get this: there are lots more kinds of phenomena like this, and they’re all caused by ice crystals in the air! The crystals have different shapes – some are flat, some barrel-shaped, so they bend light differently, and their orientation to us causes all these fantastic displays.

By coincidence, just a few days ago BABloggee Joe DePasquale (who works at the Harvard Smithsonian Center for Astrophysics) also saw an aamazing display. Here’s one of the shots he sent me:

Wow. You can see a lot of the same features as in David Hathaway’s picture, too (in fact, Joe made a diagram so you can see what’s what). BABloggee Alan French let me know that there’s a fine gallery of them on Flickr, too.

It’s possible some of this was due to ex-Hurricane Sandy getting moisture high in the atmosphere where it could freeze into crystals. But I’ll note again that I have seen many of these same haloes myself. Most are not rare at all, and all you need to do is keep your eye on the sky. Seriously, one of the first things I do on any day where there are high clouds is look near (not at!) the Sun and see if there’s anything to be seen.

Usually there isn’t. But sometimes, just sometimes, you get that amazing display that makes all the fruitless searching totally worth it.

Look up! There’s a whole Universe out there. And some of the coolest stuff is really close to home, literally just over your head.

Image credits: David Hathaway; Joe dePasquale, used by permission. Tip o’ the Snell’s Law to SpaceWeather.com and to Elwood Herring for pointing it out to me.

Related Posts:

Halo, how ya doin’ (a picture I shot myself, and one of my very first blog entries!)
Ring around the Moon
Moon doggies
A Sun pillar gooses the sky
A warm greeting for the frigid Moon

CATEGORIZED UNDER: Cool stuff, Pretty pictures, Top Post

Comments (24)

  1. Wow. This is stunning.

    Joe’s diagram is also great. It got me into thinking we can create an app for this (if one is already not there in app store/google play).

  2. tipper

    This is a result of chemtrails and is by no means a natural phenomenon. Look it up on YouTube tons of videos on this. Also very interesting that this was prevalent after Hurricane Sandy; chemtrails have been linked to weather manipulation techniques by emitting high frequency waves on areas sprayed with chemtrails.

  3. Wait, which part is caused by aliens going the speed of sound? Or is it the speed of light? Whatever, same difference. (Reality TV inside joke, sorry.)

  4. Alex W.

    Ahah! I spotted a really clear halo around the zenith a couple of months ago (actually on a pretty temperate evening) when I saw it reflected on the bonnets of some parked cars. Now I know what to call it.

    Got to keep looking up.

  5. RocketDoc

    @tipper: William of Ockham called. He would like you to remember to take your meds.

    No need to invoke large complex paranoid conspiracy theories when simple, well defined physics will provide all the explanation you need. But thank you very much for providing some much needed morning amusement.

  6. Nigel Depledge

    Such a cool pic!

    The most interesting atmospheric phenomenon I’ve seen has been parhelia or sundogs.

  7. Nigel Depledge

    @ Tipper (2) –
    Heh, a very good Poe.

    Juist a tip, though – next time you post a Poe, make sure you label it as such so that everyone knows it to be so.

  8. Beth

    Very nice pictures. I see (and photograph) some of these pretty frequently – especially sundogs, 22-degree halos, and circumzenithal arcs. But I’ve seen some of the others. One example:

    With Sandy’s moisture and the cold air pushed south, I can see why people outside Sandy’s path would get a halo treat. Sometimes you can get such nice displays at winter resorts from the snowmaking machines. It’s good to see natural ones. Unfortunately in Pennsylvania, we’re still stuck under Sandy’s leftover clouds.

    Keep looking up but block the sun.

  9. Marina Stern

    I’ve never seen that much going on at the same time.

  10. dessy

    I have been fortunate enough to have seen the 22 deg halo and sun dogs on a couple of occasions but these other artefacts are something special. Thanks BA!

  11. mike burkhart

    I’ve seen sundogs before, but none like this.

  12. Danny Caes

    I don’t know if this is already mentioned somewhere, but… I think the brightness of a sundog (Parhelion) could create its own Primary and Secondary Rainbows (if it’s raining at the opposite side of the sky). The series of small sketches of rare rainbow-like arcs on page 207 of M.G.J.Minnaert’s book ‘Light and Color in the Outdoors’ (Springer-Verlag) are perhaps observations of rainbows created by very bright sundogs. The sketch of the two complete rainbows with the red spot in them could be the crossing of the red arcs of two secondary rainbows created by two bright sundogs.
    Once I made a very accurate drawing of these possible “new” rainbow-phenomena (as they should appear in nature), and I must say, I think I might have discovered the sources of that red spot! (remember: the red part of a sundog is always the most distinct, while the bluish part is mostly a vague horizontal streak).
    I hope my discovery (the crossing of two sundog rainbows and red spot) is not “old” news.
    Thanks to Wesley Haynes (Kipp Teague’s Apollo-group) who send me this online DISCOVER-magazine page with photographs of the amazing halo display.
    Thanks Wes!

    Danny Caes,
    Ghent – Belgium

  13. Aleksandar

    Wow! To learn the such things exist. I’ve seen pics before and though to be composites or photoshops. Barely seen the most basic sun halo. I see Moon halos nearly all winter, but this… maybe saw just faint solar halo couple times in my life. Never any of “advanced” features.

  14. ctj

    am i the only one who can’t see the “Parry infralateral”?

  15. Newer seen this in real life. I am living in Ukraine.

    Your post reminds me time when I was 16 and reading Jack London. I was particularly impressed by “The Sun-Dog Trail” short story: “The northern lights flame in the sky, and the sun-dogs dance, and the air is filled with frost-dust…”, “On either side the sun are sun-dogs, so that there are three suns in the sky. The frost-dust is like the dust of diamonds, and all the air is filled with it…”

    I didn’t know what sun-dogs means back than. I was reading book in Russian, and “sun-dogs” was translated literally as “fake suns”. I thought that it was some kind of reflection from the snow.

  16. Mary

    I saw the Boston area one and I was astounded. It was by far the most complex one I’ve ever seen. I pulled my housemate out of his apartment to look and he’s still mad at me. I didn’t say to look directly into the sun…duh….

  17. Matt B.

    I can’t see the pictures in the “Joe made a diagram” link. Without that, I suspect that the “very faint white vertical oval” is actually a vesica, but if it is in fact an overlap of two circles, I can’t figure out why their centers are located where they are.

    So “heliocanesenate” is from “helio” for “sun” and “canes” for “dogs”, right? You’re mixing your Greek and Latin, Phil. It should be “heliocynenate”. (Because nitpicking a nonce word is important.!)

  18. I also ran outside to take photos of this, although my view was partially obstructed. This is one of many:


    I’ve never seen this many effects at one time, although I have seen several halos and sundogs over the years.

    Thanks for writing this up.

  19. Vincent

    That was an great picture.
    And the best part: even if it’s in the sky, it’s part of our own amazing planet.

  20. Aaron

    I can’t for the life of me see a halo matching the description of a Parry infralateral in the picture. But I do see an arc-shaped brighter area on the right side of the superlateral, but I think it matches item 21a, Upper Tape Arc, in this site you linked: http://vjac.free.fr/skyshows/icehalos/icehalos.html . Are we looking at different things, or is that one misidentified?

  21. Messier Tidy Upper

    Wow. That is just a jaw droppingly superluminous photograph!

    (Has to be one of the best images of 2012 surely! )

    Amazing what ice crystals in our sky can produce. Cheers BA. 8)

  22. W Sanders

    I live in California so it never gets cold enough for all these fun arcs to form. :-( Oh wait … :-)

  23. agenoria

    When there’s thin cloud I look out for halos etc. but I’ve never seen so many arcs and halos at one time. I find them very difficult to photograph. :(

    With the Wars of the Roses, it’s often difficult to get accurate information, but it seems likely that very bright sun dogs seen at the battle of Mortimer’s Cross in 1461 were the reason Edward IV had the sun as part of his personal badge.


    This article says that in Henry VI Part 3, Shakespeare mentions “three suns”.

    Recently, in my local county record office I found a mention of sun dogs, “mock suns”, in a farmer’s notebook, dated August 29 1774.

  24. Matt B.

    Truly, it is the Expendables of optics.


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