APOD: Saturn's Northern Hexagon (2020 Jul 05)

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APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by APOD Robot » Sun Jul 05, 2020 4:05 am

Image Saturn's Northern Hexagon

Explanation: Why would clouds form a hexagon on Saturn? Nobody is sure. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it anywhere else in the Solar System. Acquiring its first sunlit views of far northern Saturn in late 2012, the Cassini spacecraft's wide-angle camera recorded this stunning, false-color image of the ringed planet's north pole. The composite of near-infrared image data results in red hues for low clouds and green for high ones, giving the Saturnian cloudscape a vivid appearance. This and similar images show the stability of the hexagon even 20+ years after Voyager. Movies of Saturn's North Pole show the cloud structure maintaining its hexagonal structure while rotating. Unlike individual clouds appearing like a hexagon on Earth, the Saturn cloud pattern appears to have six well defined sides of nearly equal length. Four Earths could fit inside the hexagon. Beyond the cloud tops at the upper right, arcs of the planet's eye-catching rings appear bright blue.

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heehaw

Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by heehaw » Sun Jul 05, 2020 8:49 am

The most charming feature of Saturn is that if you could put it in your bathtub, it would float. Of course you wouldn't do that, because if you did, when you took it out it would leave a ring.

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by De58te » Sun Jul 05, 2020 12:08 pm

That's funny, Heehaw. But realistically, I'd imagine that with Saturn's atmospheric temperature as low as −189 °C, that the 20 gallons or so of water in your bathtub would instantly freeze to ice when Saturn touches it. My source, I don't claim to be a scientist, but I remember a school physics class where the teacher dipped a rose into a pot of liquid nitrogen (roughly the same temperature as Saturn) and the rose petals froze instantly.

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by orin stepanek » Sun Jul 05, 2020 12:33 pm

🪐 I think next to Earth; Saturn 2nd on the beautiful planet list! :saturn:
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by NCTom » Sun Jul 05, 2020 1:06 pm

Does the color enhancement indicate the cloud hexagon is a high ridge surrounding the pole region, apparently considerably higher than the interior? Can we estimate how much higher the hexagon clouds are than the pole region itself?

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by neufer » Sun Jul 05, 2020 3:14 pm

https://en.wikipedia.org/wiki/Hex_sign wrote:
<<Hex signs are a form of Pennsylvania Dutch folk art, related to fraktur, found in the Fancy Dutch tradition in Pennsylvania Dutch Country. Barn paintings, usually in the form of "stars in circles", began to appear on the landscape in the early 19th century, and became widespread decades later when commercial ready-mixed paint became readily available. The term hex with occult connotations may derive from the Pennsylvanian German word "hex" (German "Hexe", Dutch "Heks"), meaning "witch". However the term "hex sign" was not used until the 20th century, after 1924 when Wallace Nutting's book Pennsylvania Beautiful was published. Nutting, who was not a Pennsylvania native, interviewed farmers about their distinctive barn decoration. Before this time there was no standardized term and many Pennsylvania German farmers simply called the signs "blume" or "sterne" (meaning flowers or stars). However one farmer used the term "Hexefoos" in his description. The term became popular with Pennsylvania Germans themselves during the blossoming tourist trade of Southeastern Pennsylvania.

These signs were traditionally ordained with six - pointed stars. There is also the belief that the origin leading to the word "hex sign" is that English settlers mispronounced the German word for six, "sechs" as "hex".

In recent years, hex signs have come to be used by non–Pennsylvania Dutch persons as talismans for folk magic rather than as items of decoration. Some believe that both the Pennsylvania German barn design and hex designs originate with the Alpine Germans. They note that hexes are of pre-Christian Germanic origin; for instance, a circled rosette is called the Sun of the Alps in Padania (the Po Valley). Based on this history, Neopagans or Germanic heathens have taken up the practice of creating hex signs, incorporating other pre-Christian signs and symbols into the hex work. Gandee, in his book Strange Experience, Autobiography of a Hexenmeister, described hex signs as "painted prayers".

Some view the designs as decorative symbols of ethnic identification, possibly originating in reaction to 19th century attempts made by the government to suppress the Pennsylvania German language. Anabaptist sects (like the Amish and Mennonites) in the region have a negative view of hex signs. It is not surprising that hex signs are rarely, and perhaps never, seen on an Amish or Mennonite household or farm.>>
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Ann » Sun Jul 05, 2020 3:19 pm

heehaw wrote:
Sun Jul 05, 2020 8:49 am
The most charming feature of Saturn is that if you could put it in your bathtub, it would float. Of course you wouldn't do that, because if you did, when you took it out it would leave a ring.
:lol2:
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Phillip Mitchell

Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Phillip Mitchell » Sun Jul 05, 2020 4:39 pm

Re: Explanation for Saturn's Hexagon - Hint - Study Sacred Geometry, snowflakes & crystals...

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Chris Peterson » Sun Jul 05, 2020 4:59 pm

De58te wrote:
Sun Jul 05, 2020 12:08 pm
That's funny, Heehaw. But realistically, I'd imagine that with Saturn's atmospheric temperature as low as −189 °C, that the 20 gallons or so of water in your bathtub would instantly freeze to ice when Saturn touches it. My source, I don't claim to be a scientist, but I remember a school physics class where the teacher dipped a rose into a pot of liquid nitrogen (roughly the same temperature as Saturn) and the rose petals froze instantly.
Put a -189°C basketball in a bathtub filled with 20 gallons of water and it will take quite a while to freeze solid.
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Ann » Sun Jul 05, 2020 5:02 pm

NCTom wrote:
Sun Jul 05, 2020 1:06 pm
Does the color enhancement indicate the cloud hexagon is a high ridge surrounding the pole region, apparently considerably higher than the interior? Can we estimate how much higher the hexagon clouds are than the pole region itself?
For what it's worth...
Wikipedia wrote:

Saturn's hexagon is a persisting hexagonal cloud pattern around the north pole of the planet Saturn, located at about 78°N. The sides of the hexagon are about 14,500 km (9,000 mi) long, which is about 2,000 km (1,200 mi) longer than the diameter of Earth. The hexagon may be a bit greater than 29,000 km (18,000 mi) wide, may be 300 km (190 mi) high, and may be a jet stream made of atmospheric gases moving at 320 km/h (200 mph). It rotates with a period of 10h 39m 24s, the same period as Saturn's radio emissions from its interior. The hexagon does not shift in longitude like other clouds in the visible atmosphere.
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Sa Ji Tario

Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Sa Ji Tario » Sun Jul 05, 2020 7:53 pm

If anyone did not know
Saturn's strange hexagon recreated in the lab.

Saturn has one of the most geometric features in the Solar System: a giant hexagon that surrounds its north pole. Although not as famous as Jupiter's Great Red Spot, Saturn's hexagon is just as mysterious. Now, researchers have recreated this formation in the laboratory using little more than water and a turntable, an important step forward, experts say, to finally unravel this cosmic mystery.
Its striped appearance comes from the flows that fly from the west through its atmosphere to different latitudes. Most planes form circular bands, but the Voyager spacecraft captured images of a large hexagonal shape (it was passing over the planet's north pole in 1988). The surprised scientists attributed a huge storm-like vortex to its shape along one side of the hexagon, which Voyager also changed on its way. Astronomers thought that this whirlpool was altering the course of the flow, in the same way that a large rock would change the course of the nearby river. But when the Cassini mission returned to Saturn and photographed the north pole in 2006, the service was gone, but the hexagon was still there.

Physicists Ana Claudia Barbosa Aguiar and Peter Read from the University of Oxford in the UK wanted to see if they had trouble recreating the hexagon in the laboratory. Place a 30 liter water cylinder on a slow spinning table; The water represented Saturn's atmosphere rotating with the rotation of the planet. Inside this tank, place a small ring that rotates faster than the cylinder. This created a miniature artificial "flow" that the researchers followed with a green tincture.
The faster the ring turned, the less circular the green flow became. The small eddies formed along its edges, which slowly grew larger and more powerful, forced the fluid within the ring to take the shape of a polygon. By altering the speed of the ring's spin, the scientists generated various shapes. "We were able to create ovals, triangles, squares, almost any shape you want," says Leer. The greater the difference between the planet's rotation and the flow, between the cylinder and the ring, the fewer sides the polygon has, according to the team's information in this month's issue of Icarus. Barbosa Aguiar and Leer feel that the flow of Saturn's north pole rotates at a relative speed with respect to the rest of the atmosphere that favors a six-sided figure, a hexagon.
Such polygonal formations have been seen at the center of the main hurricanes on Earth, given Barbosa Aguiar, although they quickly dissipate. "Most planetary scientists are not analyzed for the ubiquity of this type of pattern in fluid dynamics."
Planetary scientist Kevin Baines of NASA's Jet Propulsion Laboratory in Pasadena, California is impressed. "These results are very interesting," he says. "The team has put together what I think is a crucial article that could withstand the test of time." Although the lab experiment doesn't explain what force directs this particular flux, it says the results give a real idea of what might actually be happening in Saturn's atmosphere.
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by ta152h0 » Sun Jul 05, 2020 7:59 pm

Just when you know everything, boom! pass the ice cold one!
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by neufer » Sun Jul 05, 2020 8:12 pm

Click to play embedded YouTube video.
Chris Peterson wrote:
Sun Jul 05, 2020 4:59 pm

Put a -189°C basketball in a bathtub filled with 20 gallons of water and it will take quite a while to freeze solid.
It takes:
  • ~397 Joules to freeze 1 cc of room temperature water.
    ~186 Joules to heat 1 cc of liquid Nitrogen to 0º C
Ergo: A 600 cc basketball full of liquid Nitrogen
could potentially freeze ~280 cc of bath water.
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Chris Peterson » Sun Jul 05, 2020 8:22 pm

neufer wrote:
Sun Jul 05, 2020 8:12 pm
Click to play embedded YouTube video.
Chris Peterson wrote:
Sun Jul 05, 2020 4:59 pm

Put a -189°C basketball in a bathtub filled with 20 gallons of water and it will take quite a while to freeze solid.
It takes:
  • ~397 Joules to freeze 1 cc of room temperature water.
    ~186 Joules to heat 1 cc of liquid Nitrogen to 0º C
Ergo: A 600 cc basketball full of liquid Nitrogen
could potentially freeze ~280 cc of bath water.
I was considering a basketball actively held at -189°C (so an active heat pump). You can still do the calculation, of course, but you have to consider the thermal conductivity of the bathtub walls to determine if the water will ever completely freeze or not.
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by bystander » Sun Jul 05, 2020 8:24 pm

Sa Ji Tario wrote:
Sun Jul 05, 2020 7:53 pm
If anyone did not know
Saturn's strange hexagon recreated in the lab.
...
Click to play embedded YouTube video.
Saturn's Hexagon Recreated in the Laboratory
Emily Lakdawalla | Planetary Society | 2010 May 04
A Laboratory Model of Saturn’s North Polar Hexagon ~ Ana C. Barbosa Aguiar et al
Know the quiet place within your heart and touch the rainbow of possibility; be
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by daddyo » Mon Jul 06, 2020 3:36 am

The interesting difference between the lab experiments of the hexagon effect and Saturn's is the lab seems to show eddies that seem to hold in the sides of the hexagon, forming it. I don't notice them on the planet images so far https://en.wikipedia.org/wiki/Saturn%27 ... oaches.gif

It could be that they don't get naturally highlighted as intentionally done in experiments, or maybe the duration of the videos aren't long enough to expose them.

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by neufer » Mon Jul 06, 2020 5:01 pm

Chris Peterson wrote:
Sun Jul 05, 2020 8:22 pm
neufer wrote:
Sun Jul 05, 2020 8:12 pm
Click to play embedded YouTube video.
Chris Peterson wrote:
Sun Jul 05, 2020 4:59 pm

Put a -189°C basketball in a bathtub filled with 20 gallons of water and it will take quite a while to freeze solid.
It takes:
  • ~397 Joules to freeze 1 cc of room temperature water.
    ~-186 Joules to heat 1 cc of liquid Nitrogen to 0º C
Ergo: A [12x]600 cc basketball full of liquid Nitrogen
could potentially freeze ~[12x]280 cc of bath water.


Note: I previously left out 1 factor of basketball [12cm] radius.
I was considering a basketball actively held at -189°C (so an active heat pump). You can still do the calculation, of course, but you have to consider the thermal conductivity of the bathtub walls to determine if the water will ever completely freeze or not.
Given a perpetual heat pump that forces the basketball to be held at -189°C
  • eventually everything must drop down to -189°C :brr:

Of course, now I MUST do the calculation....
however, I will remove the bathtub walls entirely and
place your -189°C basketball of [12cm] radius inside a swimming pool of 15°C water
(while ignoring convective and radiative heat transfers).

The basketball becomes coated with an ice shell of thickness (r-12) out to radius r
with an ice heat conductivity of 0.02 W/(K x cm)

This radius r grows at a rate:

d(r-12)/dt = 0.02 W/(K x cm) [189K/(r-12)] /[~397 Joules/cc]


So: (r-12)2/2 = 0.02 W/(K x cm) [189K] /[~397 Joules/cc] x time

Such that: the ice shell will take ~52.5 (r-12)2 seconds to grow to a radius of r.

For an ice shell out to 1 m diameter it takes: ~52.5 (50-12)2 seconds = 21 hours.
For an ice shell out to 2 m diameter it takes: ~52.5 (100-12)2 seconds = 113 hours.
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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by TheZuke! » Mon Jul 06, 2020 6:20 pm

Phillip Mitchell wrote:
Sun Jul 05, 2020 4:39 pm
Re: Explanation for Saturn's Hexagon - Hint - Study Sacred Geometry, snowflakes & crystals...
Yes, its presence is easily explained if a huge snowflake is floating just below those clouds!

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by johnnydeep » Mon Jul 06, 2020 6:32 pm

bystander wrote:
Sun Jul 05, 2020 8:24 pm
Sa Ji Tario wrote:
Sun Jul 05, 2020 7:53 pm
If anyone did not know
Saturn's strange hexagon recreated in the lab.
...

Saturn's Hexagon Recreated in the Laboratory
Emily Lakdawalla | Planetary Society | 2010 May 04
A Laboratory Model of Saturn’s North Polar Hexagon ~ Ana C. Barbosa Aguiar et al
Wow! That's quite an amazing thing to have reproduced the hexagonal cloud pattern experimentally. And that blog post is only two months old too. Thanks!
"To Boldly Go......Beyond The Fields We Know."

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by bystander » Mon Jul 06, 2020 6:37 pm

johnnydeep wrote:
Mon Jul 06, 2020 6:32 pm
bystander wrote:
Sun Jul 05, 2020 8:24 pm
Saturn's Hexagon Recreated in the Laboratory
Emily Lakdawalla | Planetary Society | 2010 May 04
... And that blog post is only two months old too. Thanks!
That blog post is 10 years old
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alive to the gentle breeze of communication, and please stop being such a jerk.
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Neil M

Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by Neil M » Thu Jul 16, 2020 1:10 am

Is it possible that this 'hexagon' is actually a flow behaving as a sine wave? Or, at least, it would appear more like a sine wave it it was at a lower latitude?

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Re: APOD: Saturn's Northern Hexagon (2020 Jul 05)

Post by neufer » Thu Jul 16, 2020 1:22 pm

Neil M wrote:
Thu Jul 16, 2020 1:10 am

Is it possible that this 'hexagon' is actually a flow behaving as a sine wave?
Or, at least, it would appear more like a sine wave if it was at a lower latitude?
This 'hexagon' might appear more like a sine wave at a lower atitude.

It might also be one large permanent convective Bénard cell "supergranule:"
https://en.wikipedia.org/wiki/Granule_(solar_physics) wrote: <<Granules on the photosphere of the Sun are caused by convection currents (thermal columns, Bénard cells) of plasma within the Sun's convective zone. The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation.

The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. (The terms darker and cooler are strictly by comparison to the brighter, hotter plasma. Since luminosity increases with the fourth power of temperature, even a small loss of heat produces a large luminosity contrast; this "cooler", "darker" plasma is still far hotter and vastly brighter than a thermite reaction.) In addition to the visible appearance, which would be explained by convective motion, Doppler shift measurements of the light from individual granules provides evidence for the convective nature of the granules.

A typical granule has a diameter on the order of 1,500 kilometres and lasts 8 to 20 minutes before dissipating. At any one time, the Sun's surface is covered by about 4 million granules. Below the photosphere is a layer of "supergranules" up to 30,000 kilometres in diameter with lifespans of up to 24 hours.>>
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