APOD: Orange Sun Scintillating (2011 Nov 15)

[APOD Robot]

Orange Sun Scintillating

Explanation: Our Sun is becoming a busy place. Taken just last week, the Sun was captured sporting numerous interesting features including one of the larger sunspot groups yet recorded: AR 1339 visible on the image right. Only last year, the Sun was emerging from an unusually quiet Solar Minimum that lasted for years. The above image was recorded in a single color of light called Hydrogen Alpha, inverted, and false colored. Spicules cover much of the Sun's face. The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening. Just over the Sun's edges, several scintillating prominences protrude, while prominences on the Sun's face are seen as light streaks. Possibly the most visually interesting of all are the magnetically tangled active regions containing cool sunspots. As our Sun's magnetic field winds toward Solar Maximum over the next few years, increased activity will likely create times when the Sun's face is even more complex.

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[Ann]

This is a beautiful and fascinating image.

Ann

[Beyond]

YES! it is. But at the same time, it does look a little like an orange starting to go bad

[neufer]

For a more Scintillating discussion go to:

http://asterisk.apod.com/viewtopic.php? ... ng#p147510

[orin stepanek]

OK; the video predicted the sun spot activity to maximise in 2010 or 2011 ar maybe even 2012; so I would conclude that the high is about behind us. meaning that solar activity should start to minimize.
http://science.nasa.gov/science-news/sc ... otlesssun/

Click to view full size image

Anyway; you can't change what the sun is doing; but you can keep in the shade. Oh; and have a cool one!

[neufer]

<<The study of [sun spot] cycles was generally popular through the first half of the century. Governments had collected a lot of weather data to play with and inevitably people found correlations between sun spot cycles and select weather patterns. If rainfall in England didn't fit the cycle, maybe storminess in New England would. Respected scientists and enthusiastic amateurs insisted they had found patterns reliable enough to make predictions. Sooner or later though every prediction failed. An example was a highly credible forecast of a dry spell in Africa during the sunspot minimum of the early 1930s. When the period turned out to be wet, a meteorologist later recalled "the subject of sunspots and weather relationships fell into dispute, especially among British meteorologists who witnessed the discomfiture of some of their most respected superiors." Even in the 1960s he said, "For a young [climate] researcher to entertain any statement of sun-weather relationships was to brand oneself a crank." >>

[zloq]

I think this is a nice looking rendering and I have seen others by him like it, but it wasn't until I read the caption that I realized something was amiss. Normally the limb is darkened, as alluded to in the caption, but the caption explains its brightening as the result of inverting and false coloring the original image. But it doesn't "look" like an inverted image - in fact, the sunspots are still dark, while the limb is indeed brighter instead of darker. I think the effect is achieved by a nonlinear - and non-monotonic - intensity mapping, which makes the appearance very non-physical - even though it is pleasing. Dark things are dark; bright things are dark; and the mid-range is brightest. At least I think that is what's going on.

It's common to apply "curves" in photoshop to bring out detail in certain ranges of brightness, but I think it is very unusual in normal photography or even astrophotography to use an intensity mapping that is non-monotonic - if that is what was done here. Usually it makes things look ugly - but in this case the sun's surface is unfamiliar enough that the resulting effect isn't jarring. In fact, I think it gives the illusion of greater detail present in the image - in the transitions from dark to bright.

The caption says bright prominences on the sun's surface show as bright in the image - but in fact the brightest features show up as dark. So, the caption is trying to talk about the physics of what's going on, with cool and hot regions, but the inconsistent intensity mapping makes this not work.

The real reason the sunspots are dark and the limb is bright here is - the use of an artistic and non-physical photoshop manipulation.

As for scintillation - I wouldn't describe the sun or the prominences in that image as 'scintillating.' I guess they are saying it is bright and shows dynamic stuff sticking out - but I wouldn't call it scintillation.

zloq

[neufer]

[size=150][color=#FF8000]In fact, [b][u]sunspots are bright[/u][/b] in Hydrogen Alpha[/color][/size]

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I think this is a nice looking rendering and I have seen others by him like it, but it wasn't until I read the caption that I realized something was amiss. Normally the limb is darkened, as alluded to in the caption, but the caption explains its brightening as the result of inverting and false coloring the original image.

But it doesn't "look" like an inverted image - in fact, the sunspots are still dark, while the limb is indeed brighter instead of darker. I think the effect is achieved by a nonlinear - and non-monotonic - intensity mapping, which makes the appearance very non-physical - even though it is pleasing. Dark things are dark; bright things are dark; and the mid-range is brightest. At least I think that is what's going on.

[Chris Peterson]

I think this is a nice looking rendering and I have seen others by him like it, but it wasn't until I read the caption that I realized something was amiss. Normally the limb is darkened, as alluded to in the caption, but the caption explains its brightening as the result of inverting and false coloring the original image. But it doesn't "look" like an inverted image - in fact, the sunspots are still dark, while the limb is indeed brighter instead of darker. I think the effect is achieved by a nonlinear - and non-monotonic - intensity mapping, which makes the appearance very non-physical - even though it is pleasing. Dark things are dark; bright things are dark; and the mid-range is brightest. At least I think that is what's going on.

No, this is what a straight inversion of an Ha image looks like. I don't see anything to suggest that a transfer curve was used that inverted some intensity zones and not others.

As for scintillation - I wouldn't describe the sun or the prominences in that image as 'scintillating.' I guess they are saying it is bright and shows dynamic stuff sticking out - but I wouldn't call it scintillation.

If you observed how this image changes over a short period of minutes or hours, you'd see the granulation pattern shifting in a way that most people would reasonably describe as "scintillating".

[zloq]

I know there are wavelengths that can make sunspots appear bright - but I also see many H-alpha images where the sunspots are dark. The key issue is - whether the raw data for these images are that way or not. Just google sun and h-alpha and you will see plenty with a dark limb and dark sunspots.

Here is just one example:

http://pro.tok2.com/~kurita/sun/2011_11/sun111112e.htm

Here is a quote from Mr. Sunspot at the National Solar Observatory:

http://eo.nso.edu/MrSunspot/answerbook/cak_ha_expl.html

"H-alpha pictures show a wide variety of features on the Sun. Plage appears brighter than average (as it does in Ca K), as do short-lived solar flares. Sunspots appear dark, as do the usually elongated filaments. "

If you follow Friedman's own links

http://www.avertedimagination.com/img_pages/AR1339.html

http://www.avertedimagination.com/img_p ... rvana.html

You can see normal looking h-alpha images with dark sunspots and a darkened limb - plus a changing relative brightness of the hot regions near the prominences. The key link is at the bottom where he has two "interpretations" of the same data - one with dark sunspots and dark limb, and the other with dark sunspots and bright limb.

My point is that it does not look like a simple inversion.

As for calling it scintillation - I think it's crazy to use that term here - either for the sun or the prominences. Busy, dynamic, active, bright - etc. It doesn't present to me any of the qualities I associate with scintillation - particularly in an astronomical context.

zloq

[Charles Mercer]

Well let me say as a novice, I couldn't help notice what appears to be a "hole" near the left side of the sunspots. Now I'm wondering could these be evidence of impacts.??? Also wonder why they are all on the left.?

[Chris Peterson]

Well let me say as a novice, I couldn't help notice what appears to be a "hole" near the left side of the sunspots. Now I'm wondering could these be evidence of impacts.??? :? Also wonder why they are all on the left.?

The "holes" ARE the the sunspots!

Sunspots and the structure around them are always left/right pairs because they reflect the different poles of the local magnetic field.

[Not A Crank]

I find this whole discussion scintillating, and not just because it's a really cool snapshot. Similes, anyone?

[artk13]

Anyone else notice the two spots that resemble the mandelbrot set? I know the resolution is low and if they were shown larger they wouldn't be perfect but the resemblance x 2 is major cool!

[neufer]

Anyone else notice the two spots that resemble the mandelbrot set?

Well... I was going to say I saw a duckie and a horsie, but I changed my mind.

[geckzilla]

I suppose the background was masked and excluded from the inversion technique. I wouldn't have suspected that it had been done.

[bactame]

Well this is an interesting image certainly in light of the observation i make in watching national news networks mentioning these events fairly often this year. But more than that the image is great; the discussion presented in the text is superb. Direct, clear and well said; easy to follow and with every link clear and to the point.

Even the post game analysis is clear and worthy of succinct understanding...thank you gentlemen.

[neptunium]

I find this whole discussion scintillating, and not just because it's a really cool snapshot. Similes, anyone?

That's not a simile. Similes are phrases that compare two objects using like, as, or other similar words. They are like phrases that make you simile , but are not as funny as jokes. If you are talking about smilies, though, then this example is as pointless as a mission to Mars without taking pictures or collecting samples.

[Beyond]

I find this whole discussion scintillating, and not just because it's a really cool snapshot. Similes, anyone?

That's not a simile. Similes are phrases that compare two objects using like, as, or other similar words. They are like phrases that make you simile , but are not as funny as jokes. If you are talking about smilies, though, then this example is as pointless as a mission to Mars without taking pictures or collecting samples.

So... A scintillating similie of a smilie, would be a frown

[Not A Crank]

I find this whole discussion scintillating, and not just because it's a really cool snapshot. Similes, anyone?

That's not a simile. Similes are phrases that compare two objects using like, as, or other similar words. They are like phrases that make you simile , but are not as funny as jokes. If you are talking about smilies, though, then this example is as pointless as a mission to Mars without taking pictures or collecting samples.

So... A scintillating similie of a smilie, would be a frown

A scintillating similie of a smilie, would be like or as a frown

[Still Not a Crank]

Neptunium is absolutely right, though. I really I meant to say 'synonyms anyone?' but guests can't edit or use proper (english) language. But what's the dif? You got it anyway.

[Beyond]

Neptunium is absolutely right, though. I really I meant to say 'synonyms anyone?' but guests can't edit or use proper (english) language. But what's the dif? You got it anyway.

Hey, in a 'Space' forum, being a few million light years off... is close enough

[zloq]

I suppose the background was masked and excluded from the inversion technique. I wouldn't have suspected that it had been done.

Yes - that seems like a possibility - but in other articles on his technique he does consistently mention "inverting" the image.

I tried some things in photoshop with his own image, and when you invert the raw Ha image, after converting it to grayscale, it takes on most of the qualities of his image except the limb brightening is relatively subdued and the sunspots are glaringly white and look 'wrong' - and go against the desired effect of a glowing, normal looking sun. The area around the sunspots (inverted view) does match pretty well his final image, though, so I no longer think there is some kind of inverted brightness function - but instead I think the sunspots are specifically altered after the inversion.

I think what must be happening is that the image is inverted and stretched a bit, and then the sunspots are manually colored in to turn them black again. This removes the main thing that gives it a boring "negative" look - and instead looks like a normal sun with a lot of detail and a glowing limb - and black, natural looking sunspots.

As an aside - there is extensive literature on measuring and "flattening" the limb darkening - since it can help model the atmosphere of the sun, and flattening is needed for consistent photometry of objects on the surface. But I don't know anyone who previously did the rendering this way - Instead of flattening the limb you make it "glow," but with black sunspots. I think the visual impact is real - but I also think there is an added step to "fix" the sunspots that isn't mentioned and is purely artistic - and makes it hard to write a caption describing the physics of the scene.

The details of the processing are also somewhat confusingly described, with cross-out corrections and a mea culpa, on Phil Plait's blog - but the detail of black sunspots that should be white, if it were a simple inversion, is not mentioned:

http://blogs.discovermagazine.com/badas ... pting-sun/

If it isn't a manual operation on selected sunspots - I think there is still some kind of "fix" in place to make the sunspots dark that is not a simple inversion of the scene.

It's interesting that all you have to do is make the sunspots black after inversion - and now the sun looks fairly normal despite the inversion. If you did the same to the pupils (manually darkened them) in an inverted image of a person's face - I don't think that would work so well - but it would probably help.

zloq

[DavidLeodis]

I appreciate that the image is an inverted H-alpha image but nevertheless, to me, "The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening" sentence is still very confusing. The information brought up through the "limb darkening" link is helpful though the illustration there does shows limb darkening unlike the APOD which is brightening to the edge!

[Chris Peterson]

I appreciate that the image is an inverted H-alpha image but nevertheless, to me, "The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening" sentence is still very confusing. The information brought up through the "limb darkening" link is helpful though the illustration there does shows limb darkening unlike the APOD which is brightening to the edge! :?

It seems logical that if you an invert an image of the Sun, the limb darkening becomes "limb brightening". Are you finding the concept of limb darkening confusing, or just the use of "darkening" when that isn't what the image appears to show?