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APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Wed Feb 17, 2021 5:07 am
by APOD Robot
Sun Pillar with Upper Tangent Arc
Explanation: This was not a typical sun pillar. Just after sunrise two weeks ago in
Providence,
Rhode Island,
USA, a photographer, looking out his window, was suddenly awestruck. The astonishment was caused by a
sun pillar that
fanned out at the top. Sun pillars, singular columns of light going up from
the Sun, are themselves rare to see, and are known to be caused by sunlight
reflecting from wobbling,
hexagon-shaped ice-disks falling through
Earth's atmosphere. Separately, upper
tangent arcs are known to be caused by sunlight refracting through falling
hexagon-shaped ice-tubes. Finding a
sun pillar connected to an
upper tangent arc is extraordinary, and, initially, took some analysis to figure out what was going on. A leading theory is that this
sun pillar was also created, in a complex and unusual way, by falling ice tubes. Few might believe that such a
rare phenomenon was seen again if it wasn't for the quick thinking of the photographer -- and the camera on his nearby
smartphone.
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Wed Feb 17, 2021 9:21 am
by JohnD
Rare, no doubt, but one of the links takes you to a site with a photo of an identical phenomenon!
https://www.atoptics.co.uk/halo/colpill.htm includes an expanation of how the hexagonal crystals do it.
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Wed Feb 17, 2021 1:02 pm
by orin stepanek
Wow; a beauty for sure! I only remember seeing 1; It was from a setting sun behind the neighbors trees!
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Wed Feb 17, 2021 1:58 pm
by smitty
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Wed Feb 17, 2021 10:38 pm
by davidhumemoore
Looks like a martini to me. Which Vonnegut said was the breakfast of champions.
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Thu Feb 18, 2021 2:58 am
by neufer
http://www.atoptics.co.uk/halo/colsolat.htm# wrote:
<<Tangent arcs alter shape as the sun's altitude changes.
When the sun is on the horizon, both upper & lower tangent arcs are narrow 'Vs'. As the sun climbs the upper tangent arc opens and then droops like a gull's wings.
When the sun reaches 29º the upper arc links with the lower to become the "circumscribed halo".
The lower tangent arc narrows and then broadens again as the sun ascends. Of course, the lower arc is below the horizon when the sun is less than 22º high. Even so, it can still be seen from mountains or aircraft.>>
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Thu Feb 18, 2021 9:37 am
by JohnD
davidhumemoore wrote: ↑Wed Feb 17, 2021 10:38 pm
Looks like a martini to me. Which Vonnegut said was the breakfast of champions.
Nah.
https://www.markarnall.com/breakfast-of-champions/
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Thu Feb 18, 2021 3:16 pm
by johnnydeep
neufer wrote: ↑Thu Feb 18, 2021 2:58 am
http://www.atoptics.co.uk/halo/colsolat.htm# wrote:
<<Tangent arcs alter shape as the sun's altitude changes.
When the sun is on the horizon, both upper & lower tangent arcs are narrow 'Vs'. As the sun climbs the upper tangent arc opens and then droops like a gull's wings.
When the sun reaches 29º the upper arc links with the lower to become the "circumscribed halo".
The lower tangent arc narrows and then broadens again as the sun ascends. Of course, the lower arc is below the horizon when the sun is less than 22º high. Even so, it can still be seen from mountains or aircraft.>>
Very cool!
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Thu Feb 18, 2021 10:44 pm
by pod_person
What a lovely photo! My pictures aren't as pretty, but I've seen tangent arcs on sun pillars three times and managed to photograph them twice.
The first time was from Mauna Kea
The second and third times were both on ferry trips in British Columbia. I only had a camera with me on one trip and by the time I got it out, the tangent arc was barely visible.
I took more shots each time of course. All of them can be seen in
this album, along with two photos of a tangent arc without a sun pillar taken from my home in Vancouver, and cell phone shots my wife took of a winter sun pillar in Saskatoon.
Re: APOD: Sun Pillar with Upper Tangent Arc (2021 Feb 17)
Posted: Fri Feb 19, 2021 8:19 pm
by BillBixby
Two days later I feel my initial reaction ca be posted. The picture is wonderful but my mind is unsure if I am seeing cleavage or the back of a plumber bent over.
