APOD: All the Colors of the Sun (2010 Jun 27)

[APOD Robot]

All the Colors of the Sun

Explanation: It is still not known why the Sun's light is missing some colors. Shown above are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The above spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our yellow-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light. The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun. Helium, for example, was first discovered in 1870 on a solar spectrum and only later found here on Earth. Today, the majority of spectral absorption lines have been identified - but not all.

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[GuestSF]

Thank you so very much.
I have the automatic wallpaper app, and as I was getting my stuff ready for tomorrow, the spectrum suddenly appeared on my screen. And a profound sense of warmth and belonging filled me. And I had to swallow hard several times. Peace and hope and love and joy for you all.

[hstarbuck]

Very cool. Until I followed the link, I did not understand how to read it because it is different from basic spectrum with absorption lines. Basically each strip covers 60 angstroms increasing from left to right then up to the next strip. with 50 strips it covers 3000 angstrom (300nm) from 400nm (violet) to 700 nm (red) and makes "complete" sense.

[neufer]

Code: Select all

                         ////
                        (o o)
.    _______________oOO__(_)__OOo____________________
.    |______|_____|_____|_____|_____|_____|_____|_____|
.    |___|____|_____|_____|_____|_____|_____|_____|____
.    |_____|_____|_____|_____|_____|_____|_____|_____|_
.    |______|_____|_____|_____|_____|_____|_____|_____|
.    |___|____|_____|_____|_____|_____|_____|_____|____
.    |_____|_____|_____|_____|_____|_____|_____|_____|_

[orin stepanek]

Code: Select all

                         ////
                        (o o)
.    _______________oOO__(_)__OOo____________________
.    |______|_____|_____|_____|_____|_____|_____|_____|
.    |___|____|_____|_____|_____|_____|_____|_____|____
.    |_____|_____|_____|_____|_____|_____|_____|_____|_
.    |______|_____|_____|_____|_____|_____|_____|_____|
.    |___|____|_____|_____|_____|_____|_____|_____|____
.    |_____|_____|_____|_____|_____|_____|_____|_____|_

If your saying that the picture looks like bricks; I agree.

[owlice]

our yellow-appearing Sun

Oh, dear.

If there are to be any fisticuffs, I hope participants will use their inflatable gloves; I was up most of the night swabbing the bridge and don't want to return to find blood on the floor (nor anywhere else)!

[NoelC]

I'm impressed that not all the lines have been identified. I realize this is a daunting task with so many, and given the overlaps and near overlaps of absorption lines of various elements. Seems like an iterative task for a computer... Is it just that we don't have very accurate measurements for some elements?

-Noel

[zbvhs]

1. Why are some broad lines fuzzed out at the edges?
2. Are some lines weak and barely visible because of low abundance of the elements producing them? Or, are they resonances of some sort?
3. Why no transmission lines (i.e., white ones)?

[neufer]

1. Why are some broad lines fuzzed out at the edges?
2. Are some lines weak and barely visible because of low abundance of the elements producing them? Or, are they resonances of some sort?
3. Why no transmission lines (i.e., white ones)?

1. Pressure broadened lines have fuzzed out "wings" proportional to the width of the lines themselves.
Also, lines that are weak & barely visible are generally mostly Doppler broadened and have very sharp wings.

2. Most lines that are weak & barely visible are so because of the low abundance of the elements producing them.

3. Almost all stellar spectral lines are transmission lines (i.e., black ones)
due to pressure broadened absorption in the cool upper photosphere.

The hotter chromosphere/corona produces emission lines (i.e., white ones)
from ionized plasma but they are usually in the ultraviolet or X-ray.

[León]

For NoelC question. "Observed chromospheric emission-line wavelengths in the Pierce (1968) solar line list are compared with wavelengths in the laboratory list of Striganov & Sventitskii (1968) and more recent laboratory lists. A large number of close wavelength agreements are found for lines of higher abundance lower Z elements, providing new assignments for unidentified solar lines and alternative, more likely assignments for some solar lines which have been ascribed to low-abundance heavy elements and rare earth elements. Wavelength coincidences are found,also for lines of the rare gas elements, raising questions of verification which are important for the general problem of abundances. A limited examination of the photospheric spectrum shows that similar new assignments can be made in that spectrum". http://adsabs.harvard.edu/abs/1995ApJS..100..473K

[moonstruck]

I studied it for a long time and will have to agree with Neufer's first anology. It's a brick wall

[RAY SR.]

Has anyone questioned the natural frequency cancellation and wavelength absorption?

[drhr]

I have to concur with the brick wall theory. But I also think the use of a prism is a 2-dimensional manner of analyzing the energy from the Sun. The prism decompresses the visible light, but does not make non-visible colors visible, they pass through and remain undetected. So I think, as in Pink Floyd's Wall, we have built a wall around ourselves and we are depriving the other colors from enlightening us.
Does the test here take into account the gases which the light has to pass through within our own atmosphere? Have we looked at it from space? I'd like to see if there is a difference.

[Chris Peterson]

I have to concur with the brick wall theory. But I also think the use of a prism is a 2-dimensional manner of analyzing the energy from the Sun. The prism decompresses the visible light, but does not make non-visible colors visible, they pass through and remain undetected.

There is no such thing as a "non-visible color". A spectrograph simply analyzes the frequency content of a light source, which fully characterizes that light in terms of "color" (which is a physiological concept, not a physical one).

Although your observation about prisms makes no scientific sense, you should be aware that this image was not made using prisms. The data were obtained with a Fourier transform spectrometer, which decomposes the light source into its frequency components using an interference technique.

Does the test here take into account the gases which the light has to pass through within our own atmosphere? Have we looked at it from space? I'd like to see if there is a difference.

Yes to both (although this particular telescope obviously hasn't been used in space). When spectrograms of astronomical objects are analyzed, they are compensated for atmospheric absorption lines and band.

[neufer]

Does the test here take into account the gases which the light has to pass through within our own atmosphere? Have we looked at it from space? I'd like to see if there is a difference.

Yes to both (although this particular telescope obviously hasn't been used in space). When spectrograms of astronomical objects are analyzed, they are compensated for atmospheric absorption lines and band.

An atmospheric ozone transmission absorption band in the orange
part of the spectrum makes green flashes more pronounced.

http://antwrp.gsfc.nasa.gov/apod/ap000507.html
http://antwrp.gsfc.nasa.gov/apod/ap040321.html
http://antwrp.gsfc.nasa.gov/apod/ap070129.html

<<Some textbooks and most web pages say that the green flash is produced by refraction under ordinary atmospheric conditions. That is not true, if it was then we would see flashes much more often.

A standard stable atmosphere gets cooler with increasing height and the air density falls smoothly and monotonically. The lower and denser portion acts as a giant lens bending rays from the setting sun towards the earth. As a result, the rays appear to be coming from a point higher in the sky and the sun appears to be raised up. Green light is refracted more strongly than red and so different coloured images of the sun become very slightly vertically separated. As the sun sinks it develops a green** upper edge and a red lower one. But the effect is small usually only visible in binoculars - do not ever look without full eye protection, even for an instant.

To make a green flash these tiny refraction effects need somehow to be considerably magnified. We need a mirage ...
..............................................................................................
Why a green edge, why not blue? Why are green flashes green? Blue light is refracted more strongly than green or red and the sun's upper edge might be expected to be rimmed with blue outside a band of green. This rarely happens because so little blue light remains in the rays of the setting sun. Blue light is strongly scattered by air molecules, small dust and aerosol particles out of the direct rays. There is a further effect: traces of ozone absorb the orange light makes the contrast between the red sun and green flashes more pronounced.>>

[Ann]

APOD Robot wrote:
our yellow-appearing Sun

(Ann just shot Otto or set off the Big Bang. Let's have a poll.)

Ann

[Helio George]

Though this has to be the greatest visible spectrum image of the Sun, the topic of Solar color can become quite, well..., colorful.

The above spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our yellow-appearing Sun emits light of nearly every color,...

From space, the Sun, with its intensity reduced, will never look yellow to the vast majority of people. But we're not in space, so yellow, at least when we more often are willing and able to see the Sun on the horizon, more often does appear to us as having some tint of yellow. But the Sun simply can not be a yellow star, at least not during its dwarf period.

...it does indeed appear brightest in yellow-green light.

It does here but that is likely due to the sensitivity of the color imaging system and not truly represenative of what is really there.

SORCE presents spectral irradiance data of the Sun almost every day. The variation in the spectrum in the visible range is quite small.

The data set I grabbed demonstrates that the peak intensity of the Sun (w-m^-2-nm^-1) is located in the blue end of the spectrum (480nm at 2095.82 w-m^-2-nm^-1).

But our eyes are better modeled using photon flux rather than wattage. Since E=hv, we must convert each value to photon flux. This changes the peak to 580nm, which, *spit*, is yellow. But this peak is much more a mere pimple since all the color intensities must be integrated to obtain a true color for our star. When this is done, white will be our result. [Perhaps "uber white" would be appropriate. ]

[orin stepanek]

I for one don't think Old Sol quite fits the White Dwarf category; but that is my opinion. This definition of a White Dwarf doesn't sound like Sol!
http://en.wikipedia.org/wiki/White_dwarf

[o_0]

I just figured it out why they had this spectrum today... it's Gay Pride Day.

[neufer]

I just figured it out why they had this spectrum today... it's Gay Pride Day.

And the only two other appearances of this APOD
were also both on Gay Pride Day (i.e., last Sunday in June):

http://apod.nasa.gov/apod/ap070624.html
http://apod.nasa.gov/apod/ap030629.html

• Gay Pride Day: 2 rainbow spectra vs 13 other APODs (1995-2009)
  Non-Gay Pride Day: 0 rainbow spectra vs ~5460 other APODs
  
  Fisher's Exact Test
  http://www.langsrud.com/fisher.htm
  ------------------------------------------
  TABLE = [ 2 , 13 , 0 , 5460 ]
  Left : p-value = 1
  Right : p-value = 0.0000070069719370384826
  2-Tail : p-value = 0.0000070069719370384826
  ------------------------------------------

<<The original gay-pride flag was hand-dyed by Gilbert Baker with his boyfriend Jomar Teng. It flew in the San Francisco Gay Freedom Day Parade on June 25, 1978. It has been suggested that Baker was inspired by Judy Garland's singing "Over The Rainbow". The flag consisted of eight stripes; Baker assigned specific meaning to each of the colours:

hot pink: sexuality
red: life
orange: healing
yellow: sunlight
green: nature
turquoise: magic/art
indigo: serenity/harmony
violet: spirit

After the November 27, 1978 assassination of openly gay San Francisco City Supervisor Harvey Milk, demand for the rainbow flag greatly increased. To meet demand, the Paramount Flag Company began selling a version of the flag using stock rainbow fabric consisting of seven stripes of red, orange, yellow, green, turquoise, blue, and violet. As Baker ramped up production of his version of the flag, he too dropped the hot pink stripe because of the unavailability of hot-pink fabric. Also, San Francisco-based Paramount Flag Co. began selling a surplus stock of Rainbow Girls flags from its retail store on the southwest corner of Polk and Post, at which Gilbert Baker was an employee.

In 1979 the flag was modified again. When hung vertically from the lamp posts of San Francisco's Market Street, the center stripe was obscured by the post itself. Changing the flag design to one with an even number of stripes was the easiest way to rectify this, so the turquoise stripe was dropped, which resulted in a six stripe version of the flag - red, orange, yellow, green, blue, and violet.>>

[Ann]

Here the Danish flag is being burned by Muslims who think that Denmark has offended their religion.

Let's hope that neither the gay flag nor the solar spectrum will be burned by people who feel that their own heterosexuality has been offended!

Ann

[neufer]

Let's hope that neither the gay flag nor the solar spectrum will be burned by people who feel that their own heterosexuality has been offended!

Whew! That's a relief.

I was afraid that you might have been burned
feeling that your own white sun had been offended!

red: life
orange: healing
yellow: sunlight
green: nature
blue: magic/Art
violet: serenity/harmony/spirit
------------------------------------

Art, proud father of a lesbian.

[owlice]

magic/Art

A fitting pair!

[neufer]

magic/Art

A fitting pair!

<<Arthur C. Clarke formulated the following three "laws" of prediction:

• 1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right.
  When he states that something is impossible, he is probably wrong.
  
  2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  
  3. Any sufficiently advanced technology is indistinguishable from magic.

The first of the three laws, previously termed Clarke's Law, was proposed by Arthur C. Clarke in the essay "Hazards of Prophecy: The Failure of Imagination", in Profiles of the Future (1962). The second law is offered as a simple observation in the same essay; its status as Clarke's Second Law was conferred on it by others.

In a 1973 revision of his compendium of essays, Profiles of the Future, Clarke acknowledged the Second Law and proposed the Third in order to round out the number, adding "As three laws were good enough for Newton, I have modestly decided to stop there." Of the three, the Third Law is the best known and most widely cited. It may be an echo of a statement in a 1942 story by Leigh Brackett: “Witchcraft to the ignorant, …. Simple science to the learned.”

Clarke's Third Law codifies perhaps the most significant of Clarke's unique contributions to speculative fiction. A model to other writers of hard science fiction, Clarke postulates advanced technologies without resorting to flawed engineering concepts (as Jules Verne sometimes did) or explanations grounded in incorrect science or engineering (a hallmark of "bad" science fiction), or taking cues from trends in research and engineering (which dates some of Larry Niven's novels). Accordingly, the powers of any future superintelligence or hyper-intelligence which Clarke often described would seem astonishing.

But in novels such as The City and the Stars and the story "The Sentinel" (upon which 2001: A Space Odyssey was based) Clarke goes further; he presents us with ultra-advanced technologies developed by hyperintelligences limited only by fundamental science. In Against the Fall of Night the human race has mysteriously regressed after a full billion years of civilization. Humanity is faced with the remnants of its past glories: for example, a network of roads and sidewalks that flow like rivers. Although physically possible, it is inexplicable from their perspective. Clarke's Third Law explains the source of our amazement as our limitation, rather than the impossibility of the technology.

In his 1999 revision of Profiles of the Future, published in London by Indigo, Clarke added his Fourth Law:
"For every expert there is an equal and opposite expert."
This is similar to Gibson's law, which holds that "For every PhD there is an equal and opposite PhD.">>

[owlice]

• 3. Any sufficiently advanced technology is indistinguishable from magic.

Ah, then, so you are sufficiently advanced technology. Finally, the pieces fall into place!