Starship Asterisk*

Orange Sun Sparking

Explanation: Our Sun has become quite a busy place. Taken only two weeks ago, the Sun was captured sporting numerous tumultuous regions including active sunspot regions AR 2036 near the image top and AR 2038 near the center. Only four years ago the Sun was emerging from an unusually quiet Solar Minimum that had 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 like a carpet. 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 filamentary 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 relatively cool sunspots, seen as white dots. Currently at Solar Maximum -- the most active phase in its 11-year magnetic cycle, the Sun's twisted magnetic field is creating numerous solar "sparks" which include eruptive solar prominences, coronal mass ejections, and flares which emit clouds of particles that may impact the Earth and cause auroras. One flare two years ago released such a torrent of charged particles into the Solar System that it might have disrupted satellites and compromised power grids had it struck planet Earth.

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The local environment is hazardous place...without Black Holes, and Super Nova.

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Their are at least two edits needed in today's Explanation:

APOD Robot wrote:... the Sun was captured sporting numerous tumultuous regions including active sunspot regions AR 2036 near the image top and AR 2036 near the center.

The first AR number can't be right. Also

The gradual brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening.

Limb brightening is caused by limb darkening?

BDanielMayfield wrote:Limb brightening is caused by limb darkening?

APOD Robot wrote: wrote:...Hydrogen Alpha, inverted, and false colored...

Emphasis added...

Yeah, I noticed "inverted" Mike, but I still think something is really flipped around here.

Inverted, false colored-- I do not care. This makes a beautiful picture. It also, in explanation, is very educational. I would just like an aurora which is widespread and visible easily below 42 degrees N latitude before this maximum ends.

When you google the phase "limb brightening" the first listing is Wikipedia's article "Limb Darkening".

Limb darkening is an actual term. Limb brightening is not. There's nothing wrong with that statement but I'll mail them about the sunspot designations.

Rather surprisingly, the overall picture here of the sun is very benevolent, almost like a steaming kettle on simmer. The scales of cosmology are truly astounding.

geckzilla wrote:Limb darkening is an actual term. Limb brightening is not.

It's only true that "limb brightening" is not a term with it's own article in Wikipedia yet, which is unfortunate. Limb brightening is less common than darkening, but is a very real effect with known causes. My copy of the textbook Introductory Astonomy & Astrophysics has listings in its index for both terms.

I love looking at the Sun's Hydrogen-alpha light through my little Coronado Personal Solar Telescope.

There is a remarkable amount of detail in today's apod. I'm curious about the choice to invert the colors in this image, everything looks backwards to me! Alan Friedman posted a correct color version of this same image on his website. That one looks right to me.

Anthony Barreiro wrote:I love looking at the Sun's Hydrogen-alpha light through my little Coronado Personal Solar Telescope.

There is a remarkable amount of detail in today's apod. I'm curious about the choice to invert the colors in this image, everything looks backwards to me! Alan Friedman posted a correct color version of this same image on his website. That one looks right to me.

I wouldn't exactly call that a correct color image, but rather a picture of the Sun taken through a yellow solar filter. (Or else it might be a picture of the Sun taken through a neutral solar filter, where the image of the Sun has afterwards been mapped as yellow.)

Ann

Anthony Barreiro wrote:I'm curious about the choice to invert the colors in this image, everything looks backwards to me! Alan Friedman posted a correct color version of this same image on his website. That one looks right to me.

Thanks for providing that image Anthony, which also looks more typical or "right" to me too. It also shows that the limb brightening of today's APOD is a photographic effect, the inversion noted in the explanation. I still maintain that the way the explanation was worded was humorously contradictory, at least on first reading.

Very interesting APOD today, enjoyed the links very much.

But wait a minute though. If today's APOD was a complete inversion like a photographic negative, shouldn't the Sunspots be bright?

BDanielMayfield wrote:But wait a minute though. If today's APOD was a complete inversion like a photographic negative, shouldn't the Sunspots be bright?

The very bright spots on today's apod are sunspots. The dark areas are plages, which normally appear brighter than the background surface of the Sun. I totally do not understand the reason to invert the colors in this image.

In how many places can AR 2036 be? Lensing? Did Einstein predict this?

Anthony Barreiro wrote:

BDanielMayfield wrote:But wait a minute though. If today's APOD was a complete inversion like a photographic negative, shouldn't the Sunspots be bright?

The very bright spots on today's apod are sunspots. The dark areas are plages, which normally appear brighter than the background surface of the Sun. I totally do not understand the reason to invert the colors in this image.

Thanks, that was very helpful Anthony. I'm with you on not getting this inversion choice, which seems to obscure rather than illuminate things.

BDanielMayfield wrote:The first AR number can't be right.

Actually I think it is the second AR number that was not correct. And I fixed it now. Apologies for the oversight. BTW here is a link to a (rotated) solar image taken on the same day and labelled: http://spaceweather.com/images2014/20apr14/hmi200.gif

- RJN

Greetings and thanks for the discussion of my image featured in today's APOD. The "normal" tonality image linked above is a good illustration of two possible variations in processing the same data - but it is an APOD dating from 2011. http://www.avertedimagination.com/img_p ... rvana.html

The full resolution version of today's APOD can be seen here: http://www.avertedimagination.com/img_p ... ersun.html

The hues in this image are not inverted, but subjectively colorized. All the details are captured in the hydrogen alpha wavelength. This could be portrayed by colorizing the image completely in the deep red, but the result would be flat as the eyes are not very sensitive to perceiving subtle detail in red. The tonality of the disk is inverted, which makes the sunspots light, the hot active regions dark and gives enhance contrast to the filaments and certain other structures of the chromosphere. Having the limb brighten towards the edge rather than darken provides, to my eye, a smoother transition to the edge prominences. To me, this portrayal is closer to what I experience with my eyes - which are amazing in their ability to perceive a much larger dynamic range than an image can display on a computer screen. I realize that some do not like the inverted details. In the end, it is an aesthetic decision of the photographer to show the sun in this context. With many cameras pointed at our star, including SDO and SOHO, we have an amazing library of solar images at our fingertips. I appreciate Robert and Jerry sharing mine with you and also hearing your comments.

alanfgag wrote:Greetings and thanks for the discussion of my image featured in today's APOD. The "normal" tonality image linked above is a good illustration of two possible variations in processing the same data - but it is an APOD dating from 2011. http://www.avertedimagination.com/img_p ... rvana.html

The full resolution version of today's APOD can be seen here: http://www.avertedimagination.com/img_p ... ersun.html

The hues in this image are not inverted, but subjectively colorized. All the details are captured in the hydrogen alpha wavelength. This could be portrayed by colorizing the image completely in the deep red, but the result would be flat as the eyes are not very sensitive to perceiving subtle detail in red. The tonality of the disk is inverted, which makes the sunspots light, the hot active regions dark and gives enhance contrast to the filaments and certain other structures of the chromosphere. Having the limb brighten towards the edge rather than darken provides, to my eye, a smoother transition to the edge prominences. To me, this portrayal is closer to what I experience with my eyes - which are amazing in their ability to perceive a much larger dynamic range than an image can display on a computer screen. I realize that some do not like the inverted details. In the end, it is an aesthetic decision of the photographer to show the sun in this context. With many cameras pointed at our star, including SDO and SOHO, we have an amazing library of solar images at our fingertips. I appreciate Robert and Jerry sharing mine with you and also hearing your comments.

Thanks for the clarification and explanation, Alan. It is a very interesting image, and I appreciate your considered choices regarding colorization, although they still make the Sun look odd to me.

Thanks for explaining the hows and whys of this image Alan. It certainly is a beautiful image which has "sparked" much thought.

Does nobody wants to clean these dark spots ?

I can now see why they call them "Sunkist" oranges"!! Beautiful photo of our Great Ball of Fire – Massive gravitationally bound plasma sphere of thermal radiation somehow just doesn't cut the mustard.

Makes me want to see other varieties – An "Orange Crush" would be an interesting sight though I hear we can't. It's only a "Fanta" see.

BDanielMayfield wrote:

geckzilla wrote:Limb darkening is an actual term. Limb brightening is not.

It's only true that "limb brightening" is not a term with it's own article in Wikipedia yet, which is unfortunate. Limb brightening is less common than darkening, but is a very real effect with known causes. My copy of the textbook Introductory Astonomy & Astrophysics has listings in its index for both terms.

I had never heard of this, especially not in relation to the sun though I could imagine it or some similar term being used to describe the way the atmosphere of some planets behaves. I now see it is used but I still don't think that the description is wrong, even if it is confusing. Alan's explanation is also helpful for clearing this up.