APOD: Detailed View of a Solar Eclipse Corona (2010 Mar 16)

[APOD Robot]

Detailed View of a Solar Eclipse Corona

Explanation: Only in the fleeting darkness of a total solar eclipse is the light of the solar corona easily visible. Normally overwhelmed by the bright solar disk, the expansive corona, the sun's outer atmosphere, is an alluring sight. But the subtle details and extreme ranges in the corona's brightness, although discernible to the eye, are notoriously difficult to photograph. Pictured above, however, using multiple images and digital processing, is a detailed image of the Sun's corona taken during the 2008 August total solar eclipse from Mongolia. Clearly visible are intricate layers and glowing caustics of an ever changing mixture of hot gas and magnetic fields. Bright looping prominences appear pink just above the Sun's limb. The next total solar eclipse will be in July but will only be visible in a thin swath of Earth crossing the southern Pacific Ocean and South America.

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[neufer]

[owlice]

Such beauty, and a vocabulary lesson, too! I had to look up caustics, which led me to another new word nephoid, and then to evolute, involute, and the term circle of confusion (which, previous to today's APOD, I'd have used to refer to the group of friends I had dinner with Sunday evening <g>). Not the first time APOD has made me wish I'd taken more math and physics in my youth.

Are the white dots showing through the corona stars, or are they artifacts from image processing/manipulation?

[Amir]

Are the white dots showing through the corona stars, or are they artifacts from image processing/manipulation?

I'd say yes, it's quite possible.
besides I've seen similar images which same dots showed Stars.
the only thing that makes me confused is that I've seen more stars in shorter exposures, to me it seems that it does not have enough star!

[BMAONE23]

Where were Venus and Mercury at the time of the eclipse?

[Chris Peterson]

Such beauty, and a vocabulary lesson, too! I had to look up caustics, which led me to another new word nephoid, and then to evolute, involute, and the term circle of confusion (which, previous to today's APOD, I'd have used to refer to the group of friends I had dinner with Sunday evening <g>). Not the first time APOD has made me wish I'd taken more math and physics in my youth.

These concepts are all very interesting, but I am doubtful that any apply to this image. I think that caustic is misused here, and no caustics are actually visible. The corona is simply too thin and diffuse to introduce significant refraction effects; what we are seeing is different intensities resulting from subtle differences in gas density.

Are the white dots showing through the corona stars, or are they artifacts from image processing/manipulation?

You'd need to consider the position of the Sun and the imager to tell for certain. The corona is dim enough that stars can be seen through it, so it's very possible that's what we're seeing.

[neufer]

Where were Venus and Mercury at the time of the eclipse?

Mercury was fairly close at about 7 solar diameters away but the bright star just one solar diameter away is probably Delta Cancri

<<Delta Cancri (δ Cnc / δ Cancri) is an orange giant star approximately 180 light-years away in the constellation Cancer. It has the traditional name Asellus Australis which in Latin means "southern donkey colt". It also have had the longest of all known star names "Arkushanangarushashutu", derived from ancient Babylonian[clarification needed] and means "the southeast star in the Crab". Since it is near the ecliptic, it can be occulted by the Moon and very rarely by planets.

Delta Cancri was involved in the first recorded occultation by Jupiter:

"The most ancient observation of Jupiter which we are acquainted with is that reported by Ptolemy in book X, chap. iii (sic), of the Almagest, ...when the planet eclipsed the star known as (Delta) Cancri. This observation was made on September 3, B.C. 240, about 18h on the meridian of Alexandria." —Allen, 1898, quoting from Hind's The Solar System).

Delta Cancri also marks the famous open star cluster Praesepe or the Beehive Cluster also known as Messier 44. In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos' Prognostica reveals:

A murky manger with both stars

Shining unaltered is a sign of rain. While if the northern Ass is dimmed By vaporous shroud, he of the south gleam radiant, Expect a south wind: the vaporous shroud and radiance Exchanging stars harbinger Boreas.
—Allen, 1898

The meaning of this verse is that if Asellus Borealis or Gamma Cancris[2] is hidden by clouds, the wind will be from the south and that situation will be reversed if Arkushanangarushashutu is obscured. There is some doubt however as to the accuracy of this as Allen notes: "Our modern Weather Bureau would probably tell us that if one of these stars were thus concealed, the other also would be." (Allen, 1898)

But Delta Cancri also acts as more than just a dubious weather guide – it is a reliable signpost for finding the vividly red star X Cancri as Patrick Moore notes in his Guidebook ‘Stars of the Southern Skies’:

“In the same binocular field with Delta [Cancri] you will find one of the reddest stars in the sky: X Cancri. It is a semi-regular variable; at maximum it rises to magnitude 5 and it never falls below 7.3 so that it can always be seen with binoculars. It looks rather like a tiny glowing coal.” —Page 146, Moore, 1994.

Delta Cancri also marks the radiant of the Delta Cancrids meteor shower.

In 1876, the possibility that Delta Cancri has a companion star was proposed.>>

[owlice]

Amir, thanks, and BMAONE23, good point. My question perhaps should have been, "What the heck are the white dots?"

These concepts are all very interesting, but I am doubtful that any apply to this image. I think that caustic is misused here, and no caustics are actually visible. The corona is simply too thin and diffuse to introduce significant refraction effects; what we are seeing is different intensities resulting from subtle differences in gas density.
...
You'd need to consider the position of the Sun and the imager to tell for certain. The corona is dim enough that stars can be seen through it, so it's very possible that's what we're seeing.

Chris, I learn a lot from Asterisk, too! Thank you!

[owlice]

neufer, merci beaucoup aussi!

[jimsaruff]

Owlice!

Just because you left high school doesn't mean you have to leave math, physics and the behavior of light behind:

http://www.atoptics.co.uk/opod.htm

The gentleman running that site posts daily, I think. He knows as much about web presentation as he does about optics, and that is a great deal.

[owlice]

jimsaruff!

I knew about http://www.atoptics.co.uk/, but not about OPOD! (I'm certain it was an APOD that first sent me to http://www.atoptics.co.uk/.)

I thank you very much!! (And oh, dear heavens, I may never get another anything done ever again!! )

[biddie67]

I have to apologize in advance since I suspect you folks think my questions inane but I do have another one: with all the fusion, burning, eruptions, whatever in the sun, does it make any kind of roaring sound that can be heard at any distance from it?

Also, that photo is awesome!!!!

[Chris Peterson]

I have to apologize in advance since I suspect you folks think my questions inane but I do have another one: with all the fusion, burning, eruptions, whatever in the sun, does it make any kind of roaring sound that can be heard at any distance from it?

The surface of the Sun (and its interior) vibrates over frequency ranges from the extreme subsonic to at least the human response range. So assuming there was a medium to carry the sound, we'd presumably hear some sort of roaring. But in order to hear it, you'd need to be immersed in the gases of the Sun itself (which can transmit sound), in which case you'd [briefly] have other things on your mind.

There is an interplanetary medium, which is very thin. Certainly, the Sun produces acoustic effects in that medium. But to hear those, you'd need to be in the vacuum of space, so once again you'd probably have other concerns (and the intensity would be below your sensitivity, in any case).

[owlice]

biddie, from Wikipedia:

Sound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.

So I'm thinking no, unless the sound receptor (whatever it might be) is in the sun, and if so, the sound receptor would be toast, and toast can't hear. (I'm sure someone will correct me if I'm wrong; at least, I certainly hope so!)

It's a perfectly respectable question, IMHO, since our earthly experience includes sound; can be hard to wrap one's head around the silence of a vacuum.
~~~~~~~~~~~~~~~~~~
Never mind!!

[biddie67]

(( laughing )) thanks for the answers!! I think I understand. Sound need a medium to travel through in order to be transmitted. Out in the vacumn of space there isn't enough "medium" that will transmit the sound in a manner that we are likely to hear anything. The only medium dense enough to transmit sound is right in the vicinity of the sun which is a location that is a "no-no" for us mere humans.

Appreciate it .....