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Dark spot in Oval BA's wake

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#1 JasonBurry

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Posted 23 November 2012 - 09:20 AM

What a great apparition of Jupiter this has been so far, and with generally cooperative skies as well!

I've been observing the giant several nights in the last couple weeks, and when the seeing cooperates, like it did last night, I've noted a very high contrast dark cloud spot in the wake of Oval BA, between BA and the GRS. It's more easily spotted than Oval BA itself, due to the great contrast, but maybe 1/3 to 1/2 as large as BA. It's easily spotted in the images from the imaging forum from last night. This one is particularly excellent (what a mindblowing image!!!):

http://www.cloudynig...5534695/page...

Does this phenomena have a particular name? It seems to have been there now for over a month.

J

#2 azure1961p

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Posted 23 November 2012 - 10:11 AM

LOL I just call it spot!

Its deceiving image versus visual because when processed it ltyooks just a little more challenging than a galillean moon shadow but it is in reality quite a few steps more difficult. In slightly better than averege CT seeing it took a hefty 303x to see it pop and it did with angular surface area resolved but it was a lot more subtle. Glad you had good seeing. CT has been doing fair to good.

Pete

#3 JasonBurry

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Posted 23 November 2012 - 10:36 AM

I've had little difficulty seeing this little disk-shaped feature at 200x, using a 12.5 and 2x barlow, when the seeing cooperates. It is certainly more subtle than a moon shadow, but I found it perhaps easier than the Oval BA, due strictly to contrast.

I've seldom gotten such frequently fine views of Jupiter as I have in the last month. Last night I was struck by the desire to attempt to sketch Jove, but I've nowhere near the skills to pull it off. There's been more fine cloud and festoon detail than I'd believed possible 2 years ago.

Utterly captivating and amazing.

J

#4 Asbytec

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Posted 23 November 2012 - 12:10 PM

This spot, not sure of it's nature, really depends on it's position relative to the meridian and the seeing.
It's barely visible, if at all, most times. More often it's a small tiny blotch. On a few occasions, I actually held it as a dark pin point. From the images, it looks pretty large. But, it is indeed much smaller than a moon shadow. Say, half the size?

I've seldom gotten such frequently fine views of Jupiter as I have in the last month.


You can say that again. Here, let me help you...

I've seldom gotten such frequently fine views of Jupiter as I have in the last month.


Jupiter has just been rocking my socks off...

#5 JasonBurry

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Posted 23 November 2012 - 12:30 PM

:) Yessir!

I've seldom gotten such frequently fine views of Jupiter as I have in the last month.

J

#6 Asbytec

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Posted 23 November 2012 - 12:43 PM

You can say that again. :)

#7 CPellier

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Posted 23 November 2012 - 01:15 PM

The spot is a cyclonic brown spot. A regular feature of the STB, although usually the cyclonic wake of BA is not that well organized. There must be a small and constrained cyclonic circulation there...

#8 Asbytec

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Posted 23 November 2012 - 08:36 PM

Okay, sort of like air pooling behind the blunt end of a car traveling down the highway, that dead zone where one might draft another car? Or is it a dark cyclonic feature unto itself? And why is it dark, where did that color come from, pumped up from Jupiter's depths? Need to do some reading, I guess.

#9 CPellier

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Posted 24 November 2012 - 06:52 AM

On any atmosphere, any high-pressure region must have a cyclonic counterpart. So, oval BA that is a strong anticyclone always has an associated low-pressure region, however its shape and aspect will change over the time. The dark spot was present last year but it was less visible, so I'm thinking that there must be another structure pushing it toward BA, this would strengthen its volume and its circulation and so it would appear smaller and darker.
As to its colour, I'm thinking that dark cyclonic spots in STB are holes in the covering white clouds ; and we are seeing brownish clouds underneath.
This is logical as they are dark in methane (CH4) band, and we can make a parallel with events such as SEB revivals (see 2010-2011) when the ephemere white covering haze is partly teared up by cyclonic brown disturbances.

#10 Asbytec

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Posted 24 November 2012 - 03:34 PM

When you mention high and low pressure, you are talking about pressure at the cloud tops, I suspect. A low pressure at the surface is high pressure at altitude. So, a cyclonic disturbance in Jupiter would be the same as on Earth, cyclonic low pressure at the surface (or realitively further down into the atmosphere) and anticyclonic high pressure in the cloud tops. In other words, rising "air."

In this case, if the dark spot is BA's higher pressure (at altitude) counterpart, then it would be a system of rising air pulling up the darker gas from deeper down. That makes sense. If BA were low pressure at altitude, then it would tend to pull the darker spot toward it, or conversely, a higher pressure system nudging it closer.

Interesting.

#11 azure1961p

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Posted 24 November 2012 - 07:36 PM

I wonder just how far this *surface* is. I know we are talking about a deeper part of the atmosphere but I wonder how far down these features go. Isn't it amazing how the flyby sat photos show a FLAT surface with no hint whatsoever of varying cloud depth. A true cross section particularly of the GRS would be an interesting thing.

Pete

#12 CPellier

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Posted 25 November 2012 - 06:59 AM

There are differences in altitude in the clouds, but in comparison with the size of the planet, they are negligible. The GRS is said to be around 5 km above the surrounding clouds of the south tropical zone (that is itself a relatively high region).
None the less, those differences make strong contrast differences when viewed through a CH4 filter, where the GRS, BA etc. are the brightest/highest features of the planet with the equatorial zone and the south polar hood.
Structures in depth remain rather a mystery I think...

#13 Ed D

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Posted 27 November 2012 - 10:44 PM

OK, so I feel like an idiot. For a while I have been reading about the oval BA and couldn't figure out what everyone was talking about.
Finally!!! :foreheadslap: And to think I have been observing it and didn't make the connection until tonight.

So, what does BA stand for?

Ed D

#14 Asbytec

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Posted 27 November 2012 - 10:52 PM

I dunno, but I think my mother in law has one. :)

Really, I think it's just a designation, like oval A1.

#15 azure1961p

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Posted 27 November 2012 - 10:59 PM

Norme,

....

Heh.


Pete

#16 JasonBurry

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Posted 28 November 2012 - 09:32 AM

Wikipedia has a good summary into Oval BA's origin and naming. I'll post it here:

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Oval BA is the official name for a red storm in Jupiter's southern hemisphere similar in form to, though smaller than, the Great Red Spot (it is often affectionately referred to as "Red Spot Jr.", "Red Jr." or "The Little Red Spot"). A feature in the South Temperate Belt, Oval BA was first seen in 2000 after the collision of three small white storms, and has intensified since then.[88]

The formation of the three white oval storms that later merged into Oval BA can be traced to 1939, when the South Temperate Zone was rent by dark features that effectively split the zone into three long sections. Jovian observer Elmer J. Reese labeled the dark sections AB, CD, and EF. The rifts expanded, shrinking the remaining segments of the STZ into the white ovals FA, BC, and DE.[89] Ovals BC and DE merged in 1998, forming Oval BE. Then, in March 2000, BE and FA joined together, forming Oval BA.

**********************************************************

J

#17 Asbytec

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Posted 28 November 2012 - 10:15 AM

Yea, was reading that. Fascinating stuff.

Do you have a reference that shows the location and direction of the jet stream(s)? I found a few, but not really what I am looking for. Wanna learn more about the rotational speeds, the systems and how they interact.

#18 Gary Osoba

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Posted 17 December 2012 - 12:46 PM

I enjoyed some good sub arc-second seeing around midnight CDST December 15/16 which provided excellent views of this feature at 257X-316X. The dark spot is elliptical and I was able to resolve the angular area and its elongation visually with certain eyepieces. Measuring the minor axis on recent astrophotos, I would estimate it to be approximately .83" in width.

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#19 Asbytec

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Posted 17 December 2012 - 01:21 PM

Wow, fascinating observation to see it (dubbed the monolith by some) as elliptical. Congratulations on some great seeing. My more crude measurements agree with yours: less than 1" second.

#20 JasonBurry

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Posted 17 December 2012 - 02:19 PM

Yup, that does sound 'bout right (I chuckled at the combination of "approximatly" and 2 sig. figures decimal arcsec's). It's definately smaller than Europa, but that's about all I can say.

That it is an ellipse is unsurprising, of course, but wonderful to be able to observe....

J






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