Is the Sun yellow?

[Ann]

Chris wrote:

But the apparent color of a star also depends heavily on the colors of reference stars around it.

I don't agree. When I checked out the colors of stars, one of my biggest disappointments was Albireo. I had expected a vividly colorful binary made up of one brashly golden-orange primary and one strikingly blue component. To my extreme disappointment, both components were really pale and washed out! The yellow primary was nowhere near as yellow as Arcturus, for example, and the blue secondary was nowhere near as blue as, say, Gamma Pegasi or Lambda Orionis.



Albireo, what a pale and boring star!



But Arcturus is nicely yellow, although it's nowhere near as red as it looks here...



And Lambda Orionis is nicely blue. This is picture brings out its actual color quite well, although I apologize for the tiny size of the picture.

Ann

[Chris Peterson]

I don't agree. When I checked out the colors of stars, one of my biggest disappointments was Albireo. I had expected a vividly colorful binary made up of one brashly golden-orange primary and one strikingly blue component. To my extreme disappointment, both components were really pale and washed out! The yellow primary was nowhere near as yellow as Arcturus, for example, and the blue secondary was nowhere near as blue as, say, Gamma Pegasi or Lambda Orionis.

And yet, I see the pair as strikingly colorful; I'd describe the yellow component as far more saturated than Arcturus, and the blue component as the most blue of any stars I observe.

Like I said, you can't really get too focused on apparent color, especially in any absolute sense, because we all see color very differently. I'm not saying your observation of Albireo is wrong in any way, only that our perceptions are quite different.

[neufer]

I have read an article perhaps in Sky & Telescope which tried to explain why we see no green stars in the sky. The magazine explained that there are green stars, that is, stars whose energy output peaks in the green part of the spectrum, but these stars are just like the Sun! So, ergo, the Sun's energy output also peaks in the green part of the spectrum, so the Sun is green!

I googled "green stars" and found the following article: http://www.astronomycafe.net/qadir/q72.html The article points out, correctly, that no stars look green because if they shine most strongly in the green part of the spectrum they look white to us.

However, the guy who wrote the article then goes on by saying that in order to peak in the green part of the spectrum the star ought to have a temperature of about 10,000 degrees. Is he crazy? Doesn't he realize that a star with that temperature will peak in the blue or even the near-ultraviolet part of the spectrum? He also said that 4000 Angstrom is in the green part of the spectrum. Doesn't he know that 4000 Angstrom is the same thing as 400 nm, and that that is in the blue part of the spectrum, near the ultraviolet? Madness!

Perhaps he is just from some scientifically backward country such as Belize:

<<Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit (1686–1736). Today, the temperature scale has been replaced by the Celsius scale in most countries.

It is still in use in the United States and a few other nations, such as Belize.>>

But at least he is right about the fact that there are indeed green stars, stars which peak in the green part of the spectrum, but they look white to us - like the Sun!



Are there no green stars? Yes, actually, the Sun is one!

• --------------------------------------------------------------
  "I only know that your ladyship will do well to bear in mind that as
  we were flying by enchantment so I might have seen the whole earth and
  all the men by enchantment whatever way I looked; and if you won't
  believe this, no more will you believe that, uncovering myself
  nearly to the eyebrows, I saw myself so close to the sky that there
  was not a palm and a half between me and it. And it so happened
  we came by where the seven goats are . . ."
  
  Don Quixote replied,
  "we could not have reached that heaven where the seven goats
  Sancho speaks of are without being burned; and as we were
  not burned, either Sancho is lying or Sancho is dreaming."
  
  "I am neither lying nor dreaming," said Sancho;
  "only ask me the tokens of those same goats, and
  you'll see by that whether I'm telling the truth or not."
  
  "Tell us them then, Sancho," said the duchess.
  
  "Two of them," said Sancho, "are green, two blood-red,
  two blue, and one a mixture of all colours."
  
  "An odd sort of goat, that," said the duke; "in this earthly
  region of ours we have no such colours; I mean goats of such colours."
  --------------------------------------------------------------
  [Setting: Coffee Shop]
  
  JERRY SEINFELD: I think Superman probably has a very good sense of humor.
  
  GEORGE COSTANZA: I never heard him say anything really funny.
  
  JERRY: But it's common sense. He's got super strength, super speed.. I'm sure he's got super humor.
  
  GEORGE: You would think that, but either you're born with a sense of humor, or you're not. It's not going to change even if you go from the red sun of Krypton all the way to the yellow sun of the Earth.
  
  JERRY: Why? Why would that one area of his mind not be affected by the yellow sun of Earth?
  
  GEORGE: I don't know but he ain't funny.
  --------------------------------------------------------------

[Ann]

And yet, I see the pair as strikingly colorful; I'd describe the yellow component as far more saturated than Arcturus, and the blue component as the most blue of any stars I observe.

Yes, I realize that most people respond to Albireo the way you do, but I think I have a bit of an "absolute" color sense, at least when it comes to hue and saturation. The two components of Albireo immediately struck me as unexpectedly pale. I checked their B-V index, and here they are: For the primary component, the Johnson B-V index is 1.088 +-0.002, which is quite pale. For the blue component, the Johnson B-V index is -0.095 +-0.009, which isn't that impressive. For Arcturus, the Johnson B-V index is 1.239 +-0.006, clearly yellower than for Albireo A. For Lambda Orionis the Johnson B-V index is -0.160 +-0.025, much bluer than Albireo B. Not only do Arcturus and Lambda Orionis look yellower and bluer than Albireo A and B to me, but I can prove that they are yellower and bluer, too!

Ann

[Chris Peterson]

Yes, I realize that most people respond to Albireo the way you do, but I think I have a bit of an "absolute" color sense, at least when it comes to hue and saturation. The two components of Albireo immediately struck me as unexpectedly pale. I checked their B-V index, and here they are: For the primary component, the Johnson B-V index is 1.088 +-0.002, which is quite pale. For the blue component, the Johnson B-V index is -0.095 +-0.009, which isn't that impressive. For Arcturus, the Johnson B-V index is 1.239 +-0.006, clearly yellower than for Albireo A. For Lambda Orionis the Johnson B-V index is -0.160 +-0.025, much bluer than Albireo B. Not only do Arcturus and Lambda Orionis look yellower and bluer than Albireo A and B to me, but I can prove that they are yellower and bluer, too!

It is important to remember, however, that there is no real connection between the color we see and color indexes. These are completely different definitions of color. Fundamentally, color is a perceptual quality. Attempts to use the term in rigorous ways are quite disconnected from perception. For instance, two stars with exactly the same color indexes (indeed, with identical spectra) will be perceived as different colors if their intensities are different, because intensity is an important part of color. That's why we consider red and brown to be different colors, when they can be, in fact, identical from a spectral standpoint.

As a photometrist, I talk about star color all the time, but I am not referring to color as we generally see it.

[Ann]

By the way, thank you for your Don Quixote and Seinfeld references. I'm not absolutely sure what they meant, but I always appreciate a chance to feel cuturally sophisticated. It so happens that I like Superman too, at least when he spends his days with Lois Lane. (Get that Tom Welling boy away from me!)

The yellow (make that white) Sun of the Earth would increase Superman's humour, eh? Yes, well, I guess it doesn't work. And now to something completely different, I am the owner of an obscure and learned book about physics, a book which I bought for its delightfully quirky illustrations, since I generally don't understand physics. But there was an illustration in it which explained how the yellow (make that white) star the we are in orbit around actually decreases the entropy on the Earth: If I remember correctly, the book argued that fewer photons reach the Earth from the Sun than leave the Earth and disappear into space. That was because the photons from the Sun were more energetic than the photons that are radiated back into space from the Earth, and so those supernumerary photons brought some entropy with them out into space and dissipated it there. Or something. It sounded neat when I read it.

So maybe it's not only Superman that gets a super-boost from the Sun. Or maybe it's all in our dreams.

Hey, I think this picture actually illustrates the concept I was talking about!



But don't you think it's a good thing for us that the Sun isn't even yellow but green instead, since green photons ought to be even more efficient than yellow ones at generating large numbers of infrared photons that can carry away entropy from the Earth? Who'd'a thunk that color could be such a powerful weapon against death and decay and the arrow of time?

Ann

[Ann]

As for Albireo, let me say that when I see that star I don't compare the color of the two components with each other, I compare the yellow component with other yellow stars that I see "in my mind's eye", and the blue component with other blue stars whose color I remember. That is why I was unimpressed and disappointed with Albireo, because I really and truly thought that neither the yellow nor the blue component "measured up very well" when I compared them with other yellow and blue stars whose color I remembered. And hey, if the B-V indexes agree with me, I'm not complaining!

Ann

[The Code]

Hey Chris,

Did we not have this conversation about the color of stars a few months back?

I told you then, That I thought suns, and stars should be the whole colors of the rainbow. And my reason for asking was Mass
The heavier the star, the more color shifted it should be. This means that gravity and speed can change the color.

Thanks Ann.

[Chris Peterson]

I told you then, That I thought suns, and stars should be the whole colors of the rainbow.

The peak color can be any color of the rainbow, but the apparent color can't, as a consequence of the shape of a blackbody curve.

And my reason for asking was Mass
The heavier the star, the more color shifted it should be. This means that gravity and speed can change the color.

The most massive stars can barely shift their spectra to a degree that we can measure the effect. It is nowhere near enough to be visible. Also, a spectral shift towards either red or blue will not necessarily make a star appear redder or bluer- it depends also on what is being shifted into the visible range from outside it.

No visible stars have high enough velocities with respect to us to have much effect on their apparent color (due to Doppler shift), and stars that are far enough away to be cosmologically redshifted can't be seen with the eye at all.

[neufer]

I am the owner of an obscure and learned book about physics, a book which I bought for its delightfully quirky illustrations, since I generally don't understand physics. But there was an illustration in it which explained how the yellow (make that white) star the we are in orbit around actually decreases the entropy on the Earth: If I remember correctly, the book argued that fewer photons reaches the Earth from the Sun than leaves the Earth and disappears into space. That was because the photons from the Sun were more energetic than the photons that are radiated back into space from the Earth, and so those supernumerary photons brought some entropy with them out into space and dissipated it there. Or something. It sounded neat when I read it.

Quite right. We don't get really any energy from the sun that we don't give back in full to space (at least, prior to global warming that is).

Rather we receive low entropy from a few well directed high energy solar photons which can then be turned in useful work by replacing them with many (24 to one!) poorly directed low energy photons. (That Sun of ours is a real sucker!)

But don't you think it's a good thing for us that the Sun isn't even yellow but green instead, since green photons ought to be even more efficient than yellow ones at generating large numbers of infrared photons that can carry away entropy from the Earth? Who'd'a thunk that color could be such a powerful weapon against death and decay and the arrow of time?

Green photons mostly go to waste, unfortunately,
since they are reflected by green leaves.

What we really need is the red sun of my own home planet of Krypton

<<Not all wavelengths of light can support photosynthesis. The photosynthetic action spectrum depends on the type of accessory pigments present. For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with peaks for violet-blue and red light.>>

[Ann]

For example, in green plants, the action spectrum resembles the absorption spectrum for chlorophylls and carotenoids with peaks for violet-blue and red light.

So our plants would do even better with the violet-blue light of blue (not white) Vega, then?

Ann

[Chris Peterson]

So our plants would do even better with the violet-blue light of blue (not white) Vega, then?

I'd guess not. Most photosynthetic reactions are very dependent on the long wavelength (red/near IR) absorption band of chlorophyll species. These pigments have evolved to work well with our sunlight. Vega, with its higher output of blue compared with red is not likely to match the tuning of chlorophyll. And its high UV output would probably damage the DNA of any Earth plants growing nearby.

[Ann]

Note, however, that Vegans can only see GREEN.

Belatedly:

Chris wrote:

Sometimes G stars are called yellow stars. In terms of visual appearance, the Sun is white. In terms of stellar classification, it is yellow. Again, I don't see the problem.

What's the problem, Chris? Well, the problem is this:

http://www.physics.hku.hk/~nature/CD/re ... n_proj.jpg

http://www.asc-csa.gc.ca/images/sts-097 ... shades.gif

http://farm1.static.flickr.com/97/27102 ... f469df.jpg

http://thumbs.dreamstime.com/thumb_250/ ... edC15a.jpg

http://www.siriuscoyote.org/Photos/Hold ... %20sun.jpg

http://www.emc.cmich.edu/sunsafety/sun-for-web.gif

http://thingsthatarerectangles.files.wo ... copy15.jpg

What's the problem, Chris? The problem is partly that people have a completely mistaken idea about the color of the Sun.

But the worst problem is that astronomy feeds the misconception about the color of the (white or green) Sun by driving home the message is that it is yellow!



Ann

[Chris Peterson]

What's the problem, Chris? The problem is partly that people have a completely mistaken idea about the color of the Sun.

But the worst problem is that astronomy feeds the misconception about the color of the (white or green) Sun by driving home the message is that it is yellow!

But as directly viewed from the ground, the Sun is perceptually yellow! So all these images are actually correct, other than being too saturated. It is from space that the Sun will be seen as white, and it is the light cast on the ground by the Sun and the sky that is white. We see the Sun with its shorter wavelengths scattered away by the atmosphere, so it isn't white anymore.

[Ann]

But as directly viewed from the ground, the Sun is perceptually yellow!

You mean, when you stare at the Sun to ascertain its color?

So all these images are actually correct, other than being too saturated.

"Too saturated" is only their middle name. I, too, admit that the light of the Sun has been reddened by passing through the blue reflection nebula that is the Earth's atmosphere. So, yes, as seen from the Earth, direct sunlight has a slightly yellowish cast.

But saturation is another matter, even when seen from the Earth! And astronomy feeds the idea of a dandelion-yellow Sun by driving home the message of the yellow Sun.



The color and saturation of the light of the Sun?

Ann

[owlice]

I think Chris summed it up nicely:

It is important to remember, however, that there is no real connection between the color we see and color indexes. These are completely different definitions of color.

Ann, I'm sorry, but I'm unclear on what the issue is. You don't want children coloring the suns they draw yellow? Or do you want astronomers to change the color indexes to suit your perception of star colors? I feel I'm missing something here; please help! Thanks!

[Ann]

Good question, Owlice. To be honest, I'm frustrated about the way that everything is "shifted to the red" in astronomy, and now I'm not talking about what we know as redshift! No, my problem is that blue stars like Vega are described as white (that's a shift to the red), white stars like the Sun are described as yellow (that's a shift to the red), yellow stars like Arcturus are described as red (that's a shift to the red), pale coppery stars like MuCephei are described as blood red (that's a shift to the red), generally blue stars like hot burnt out stellar cinders are described as white dwarfs (that's a shift to the red) and truly red failed stars" are described as brown, because astronomy has run out of terms of redness to describe them.

No, honestly, I'm not bothered by the fact that children draw pictures of the Sun as yellow, of course not! But I am bothered when astronomers encourage adults to believe that the Sun is about as yellow as it looks in children's drawings.

My annoyance has everything to do with astronomy's eagerness to enhance the red color of space and "drive everything toward the red". This picture of the Gamma Cygni region may help explain what I mean:



Here you see a lot of incredibly red nebulosity and a number of white stars. Okay, but aren't emission nebulae red? Yes, they are, but their red color can't even be detected by human color vision. We can't see the redness of of these nebulae. Yet today's astrophotography enhances and brings out as much redness as it can in these nebulae images.

Yet the color of the stars is very white in this picture. Today's astrophotography does not necessarily bring out the color of the stars (all right, yes, some astrophotographers really do). But there is an underlying feeling among many astronomers that it is okay if stars look white, because they look colorless anyway, but nebulae have to be brilliantly red, because that redness is there even if we can never see it. (And red stars - that is, K- and M-class stars, should not look white, because that would be a shame since these stars are so nicely colored. That is, they are red, although they aren't.)

So we are encouraged to think of the universe as redder than it is, or as redder than we can perceive it. And that also means that we are required to think of the Sun as redder than it is. I don't like it.

Ann

[Chris Peterson]

To be honest, I'm frustrated about the way that everything is "shifted to the red" in astornomy, and now I'm not talking about what we know as redshift!

I simply don't see this happening.

Here you see a lot of incredibly red nebulosity and a number of white stars. Okay, but aren't emission nebulae red? Yes, they are, but their red color can't even be detected by human color vision. We can't see the redness of of these nebulae. Yet today's astrophotography enhances and brings out as much redness as it can in these nebulae images.

Yet the color of the stars is very white in this picture. Today's astrophotography does not necessarily bring out the color of the stars (all right, yes, some astrophotographers really do). But there is an underlying feeling among many astronomers that it is okay if stars look white, because they look colorless anyway, but nebulae have to be brilliantly red, because that redness is there even if we can never see it.

As you say, the nebula is red. If we restricted these images to what the eye sees, everything would be shades of gray, and a lot of information would be lost. An image like this is designed to represent the color of the object as we'd see it if our eyes were simply more sensitive. You are completely wrong about astronomers or imagers considering it "okay" if stars are white. In fact, it is extremely difficult to get stars to show something other than white in a field with a dim extended object, but imagers try very hard to do so. And many succeed. It would be better to say that when the nebula is the goal, most imagers are willing to live with white stars if technical limitations prevent them from displaying them in accurate color.

[owlice]

But I am bothered when astronomers encourage adults to believe that the Sun is about as yellow as it looks in children's drawings.

Describing and classifying are two different things; it seems to me your frustration may come from refusing to recognize that. Maybe your "absolute color sense" makes it difficult for you to separate the two; perhaps this is analogous to someone's with perfect (or absolute) pitch being bothered when singing or playing (early music) at A415 Hz rather than the modern tuning of A440 Hz. (I have only the testimony of others as to the bother of different As, as I have relative, not perfect, pitch, and don't much care which the tuning is, only that it is done, especially in the violin section.)

Just because there's a Metro line in DC known as the "Red Line" doesn't mean the rails/cars/etc. are literally red. I'm pretty sure most adults can deal with that, and with a star's classification as "yellow" though it might be described as "white."

[Ann]

Maybe your "absolute color sense" makes it difficult for you to separate the two; perhaps this is analogous to someone's with perfect (or absolute) pitch being bothered when singing or playing (early music) at A415 Hz rather than the modern tuning of A440 Hz.

Interesting. I think you are right.

When I had access to a moderately large telescope, I spent almost all my time on it checking out the color of stars. The more I learnt the color of stars, the more the stars became "real" to me. And when the stars became "real" to me, so did galaxies, because they are made up of stars.

I have a tremendous difficulty with with planetary nebulae. I have never been able to spot color in any of the rather few planetaries I have watched myself. The Ring looked like a grey smoke ring to me. Ho hum. So when I watch the wild and crazy array of pictures of planetary nebulae, where they have been ascribed totally unpredictable colors, I feel as if these planetaries are disconnected from reality. They frankly don't feel real to me.



Which of these planetary colors are real, pray tell?

The worst thing is that I can't imagine the true colors of the planetaries myself. With stars I feel that I can pin down their true color as long as I know their spectral class, but with planetaries I am stumped. I know that planetaries often contain a lot of OIII radiation, which is blue-green, and obviously it also contains a lot of red HII emission. But what is the proportion between these two kinds of radiation, which will produce rather radically different colors? Since I don't know, planetaries lack what to me is the all-important "color quality", and so they become uninteresting to me. I never read anything about planetaries.

My color sensitivity also means that while I almost invariably admire every picture produced by the Hubble telescope, I rarely like them all that much. That is because the Hubble people play fast and loose with color and produce color pictures that mock what I consider to be "true color". Often, but not always, the problem is that the object imaged is not made to look as blue as it should. One of my least favorite Hubble images ever is the one of starburst galaxy NGC 3310. As a starburst galaxy, NGC 3310 is very blue, and its blue color is mainly broken by pink HII nebulae. That is what NGC 3310 "ought" to look like, I think. But that is certainly not what it looks like in the portrait made by Hubble.



In this picture, the arms of NGC 3310 are a too pale blue, the arms contain no pink nebulae, parts of the arms are all white, and the nucleus of the galaxy is surrounded by a ridiculously red "lens" or ring. It looks awful, if you ask me. What makes the situation worse is that NGC 3310 is a relatively rarely photographed galaxy, so the Hubble picture becomes the "standard image" of it. As I was looking for images of NGC 3310, I found this one, where the skewed color balance of the Hubble image has been exaggerated. Grrr!



That's awful, if you ask me.

But while Hubble made NGC 3310 look much too non-blue, it made yellow galaxy M 104 look far too blue. Actually these two galaxies are made to look much the same color, except that M104 lacks NGC 3310's shocking red center!



A blue-looking M 104. Gaaah.

So I guess you are right, Owlice, "true color" is so important to me that I can't appreciate anything that mocks my color sensitivity.

Ann

[owlice]

Often, but not always, the problem is that the object imaged is not made to look as blue as it should.

As blue as you think it should. What you see is not necessarily what other people see. What you term "true color" is true... to you. I say this because of this:

With stars I feel that I can pin down their true color as long as I know their spectral class

BTW, I asked my son what color the sun is, and he said, "Yellow." I submit this as the "true color" of the sun because he is 16, and thus, knows everything!

[Ann]

As blue as you think it should. What you see is not necessarily what other people see. What you term "true color" is true... to you.

Point taken. But do you think, all things considered, that it is a good idea to show the overall stellar populations of NGC 3310 and M 104 as having the same color, although NGC 3310 is bursting with young hot stars and M 104 is almost entirely made up of old yellow stars?

I think that the Hubble people may have "shifted the color balance of NGC 3310 to the red" in order to catch the very youngest clusters it contains. They may have made NGC 3310 as non-blue as that in order to find out more facts about it. I can sympathize with that ambition, most definitely so, although I can barely stand the picture.

But why would they make M 104 so blue? Is that because they were trying to find any young clusters that the galaxy contains? If so, then again I can understand and sympathize with the scientific ambitions. But again, I dislike the picture because of the jarring color balance of it. Remember, Owlice, your son says that the Sun is yellow (and of course he would say that, since that is what he has been told all his life), but most of the light of M 104 comes from stars that are yellower than the Sun. If you view the Hubble image of M 104 as a portrait of a collection of stars that are mostly yellower than the Sun, do you think that it is a good picture?

Ann

[owlice]

I was with someone once who described something we were looking at as "blue." Blue?? That??? I had to make sure we were looking at the same thing, because the object was not what I would have described as "blue," at all! It was -- to me -- a greenish grey. I would never have called it blue. We were each unsuccessful at getting the other to admit the object should be described as we each perceived (or perhaps labeled) it.

[neufer]

• -------------------------------------------
  . Romeo and Juliet Act 1, Scene 1
  
  BENVOLIO. Madam, an hour before the worshipp'd SUN
  . Peer'd forth the GOLDEN window of the east,
  -------------------------------------------
  . The Rape of Lucrece Stanza 4
  
  O happiness enjoy'd but of a few!
  And, if possess'd, as soon decay'd and done
  As is the morning's silver-melting dew
  Against the GOLDEN splendor of the SUN!
  .................................
  Or if thou wilt permit the SUN to climb
  His wonted height, yet ere he go to bed,
  Knit poisonous clouds about his GOLDEN head.
  -----------------------------------------------
  King Richard III Act 5, Scene 3
  
  RICHMOND: The weary SUN hath made a GOLDEN set,
  . And by the bright track of his fiery car,
  . Gives signal, of a goodly day to-morrow.
  -------------------------------------------
  . King Richard II Act 1, Scene 3
  
  HENRY BOLINGBROKE: Your will be done: this must my comfort be,
  . SUN that warms you here shall shine on me;
  . And those his GOLDEN beams to you here lent
  . Shall point on me and gild my banishment.
  -------------------------------------------
  . King Henry V Act 2, Scene 4
  
  KING OF FRANCE: Up in the air, crown'd with the GOLDEN SUN,
  . Saw his heroical seed, and smiled to see him,
  . Mangle the work of nature and deface
  . The patterns that by God and by French fathers
  . Had twenty years been made.
  -------------------------------------------
  . Love's Labour's Lost Act 4, Scene 3
  
  FERDINAND: [Reads]
  . So sweet a kiss the GOLDEN SUN gives not
  . To those fresh morning drops upon the rose,
  . As thy eye-beams, when their fresh rays have smote
  . The night of dew that on my cheeks down flows:
  . Nor shines the silver moon one half so bright
  . Through the transparent bosom of the deep,
  . As doth thy face through tears of mine give light;
  . Thou shinest in every tear that I do weep:
  -------------------------------------------
  . Titus Andronicus Act 2, Scene 1
  
  AARON. Now climbeth Tamora Olympus' top,
  . Safe out of fortune's shot; and sits aloft,
  . Secure of thunder's crack or lightning flash;
  . Advanced above pale envy's threatening reach.
  . As when the GOLDEN SUN salutes the morn,
  . And, having gilt the ocean with his beams,
  . Gallops the zodiac in his glistering coach,
  . And overlooks the highest-peering hills;
  ---------------------------------------------------------------------------------
  Back to the Future Part III (1990)
  
  Buford "Mad Dog" Tannen: I think you ain't nothin' but a gutless YELLOW turd!
  . And I'm givin' you to the count of ten to come out here and prove I'm wrong! One...
  
  Marty McFly: Doc... Come on. Sober up, buddy. Let's go. Come on.
  
  Buford "Mad Dog" Tannen: Two...
  
  Saloon Old-Timer #1: You gotta get out there, SON.
  . I got $20 GOLD bet on you, so don't let me down.
  
  Buford "Mad Dog" Tannen: Three...
  
  Saloon Old-Timer #2: I got $30 GOLD bet again' you, so don't let me down.
  
  Buford "Mad Dog" Tannen: Four...
  
  Saloon Old Timer #3: You better face up to it, SON, 'cause if you don't go out there...
  
  Marty McFly: What?
  
  Saloon Old Timer #3: Everybody everywhere will say,
  . "Clint Eastwood is the biggest YELLOW-belly in the west."
  
  Buford "Mad Dog" Tannen: You hear me, runt?
  . I said that's ten, you gutless, YELLOW, pie-slinger!
  
  Marty McFly: [thinks] I don't care what Tannen says.
  . And I don't care what anybody else says, either!
  ----------------------------------

[Chris Peterson]

I have a tremendous difficulty with with planetary nebulae. I have never been able to spot color in any of the rather few planetaries I have watched myself. The Ring looked like a grey smoke ring to me. Ho hum. So when I watch the wild and crazy array of pictures of planetary nebulae, where they have been ascribed totally unpredictable colors, I feel as if these planetaries are disconnected from reality. They frankly don't feel real to me.

It isn't the intent of most scientific astronomical imagers to produce results that show some sort of actual color. The intent is to ascertain what makes up objects, and to see structure. The nebula images you include were not even made in color bands that approximate those of the eye. Those images show the structure and position of key elements in the nebulas. The idea of "true color" in such images is completely meaningless.

My color sensitivity also means that while I almost invariably admire every picture produced by the Hubble telescope, I rarely like them all that much. That is because the Hubble people play fast and loose with color and produce color pictures that mock what I consider to be "true color"...

Often that is for the reason I describe above. However, they also release many RGB images that are mapped to human color response, especially for galaxy images. The images you link, especially NGC 3310 and M104 are, in fact, carefully color balanced to reflect their true colors if our vision were more sensitive. I think you are mistaken about these being unrealistically blue or red. Images like this are usually color calibrated by adjusting the weights of the red, green, and blue channels until the colors of the surrounding stars are accurately matched.