The boiling, erupting Sun

By Phil Plait | October 28, 2010 7:00 am

I keep thinking there’s nothing new under the Sun– or on it. With SOHO, and SDO, and a thousand other telescopes pointed at it, it would take something pretty freaking cool to surprise me.

Well then. Surprise!


Holy solar retinopathy! That’s the Sun?

Yup. But this is not a space-based image from some bazillion dollar observatory! This phenomenal picture was taken by astrophotographer Alan Friedman with this relatively small (but very, very nice) ‘scope. He shot it on October 20th, and it shows our nearest star in the light of hydrogen, specifically what astronomers call Hα (H-alpha). I’ll get to that in a sec…

In this picture you can see sunspots, giant convection cells, and the gas that follows magnetic loops piercing the Sun’s surface. When we see them against the Sun’s surface they’re called filaments, and when they arc against the background sky on the edge of the Sun’s disk they’re called prominences.

The image he took is amazingly high-resolution! He has two closeups, one of the filament and sunspot near the edge of the disk on the left, and the other of prominences leaping up off the edge and silhouetted against the sky:


alanfriedman_proms_earthWow, that’s breathtaking! They look so delicate, probably because they make the Sun look fuzzy, like a comfy blanket… but have no doubts on the fury and scale of what you’re seeing here. See that little bright spot on the plume on the left, just above the Sun’s edge? That spot is the same size as the Earth. The image to the right should make that fairly clear; I made the Earth pretty close to the right size for comparison. Our planet is about 13,000 km (8000 miles) in diameter, so that one minor prominence is roughly 50,000 km high. That’s 30,000 miles. And it’s positively dwarfed by the Sun itself. A million Earths could fit inside the Sun.

In case you woke up today feeling important.

I want to note that there’s a freaky optical illusion I get when I look at the top picture: if I look at one part, say the right hand edge, then quickly move my eye to the top, it appears as if the whole disk of the Sun shrinks for a moment. It’s one of those really weird illusions that’s very difficult to pin down. Anyone else see it?

Now, about that picture and how it works…

The Sun’s surface puts out light at all wavelengths, but the surface isn’t solid. It’s a gas, and it tapers off with height. Normally, a thin gas in space emits light at very specific colors as electrons jump from one energy level to another in the individual atoms. But compressed gas in the thicker, denser part of the Sun mashes together all those energies, spreading them out, so it emits white light (that layer of the Sun is called the photosphere). Above that layer, where the gas is thinner (in a layer called the chromosphere), the hydrogen does emit light at specific colors. One of these, Hα, is in the red part of the spectrum, and in fact hot, thin hydrogen emits very strongly in Hα.

By plopping a filter in front of a telescope, you can block a lot of the light from the photosphere but let light from the chromosphere through. That’s what Alan Friedman did — he used a filter that let through a very narrow range of colors centered on Hα — to get this stunning picture. Well that, plus quite a bit of image processing! But everything you’re seeing there is real, and is happening on the Sun.

[Update: well, mea culpa: the next paragraph is wrong. I got a note from Alan: he inverted the picture of the disk of the Sun to enhance contrast. I didn’t realize this, and assumed it was natural. I knew the Sun was naturally limb-darkened in visible light due to the way gas absorbs and emits light, and also that the chromosphere was thin, so it made sense to me that in Hα the Sun would be limb-brightened. Worse, I’ve done a lot of work with nebulae and other objects that are thin shells of gas, making them limb-brightened too. All this together led me to write the following paragraph, which turns out to be incorrect! My apologies for that, and hope it hasn’t confused anyone! Now I’m off to figure out just why what I said was wrong, and the Sun is limb darkened even in Hα.]

Oh– see how the Sun gets brighter near the edge and darker in the middle? That’s not an illusion, it’s real. The gas emitting Hα light is like a thick shell surrounding the Sun’s surface (like an atmosphere). When we look straight down on the middle of the Sun we’re looking through a few thousand kilometers of it, but as you look closer to the edge you’re seeing through more and more of the gas. The more gas you see, the more light it emits, so the edge looks brighter. In white light, the opposite is true; the Sun is dark at the edges… but that’s complicated enough that I’ll just send you here to find out why.

All in all, an amazing and somewhat unsettling picture of a star seen close up. And it’s funny: there’s nothing in this picture I didn’t know about, or have some familiarity with. But somehow, the way Alan presents it, this picture really is amazingly different.

I like seeing familiar things in new ways. It jolts me out of complacency. What more can a skeptical scientist ask for?

Tip o’ the sunshade to Jason Major, and of course Alan Friedman for giving me permission to post his images!

Related posts:

SDO lunar transit: now with video!
The Sun rises again
One solar piece of flare
Solar storms coming our way this week?
Two solar ISS transits!

CATEGORIZED UNDER: Astronomy, illusion, Pretty pictures

Comments (85)

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  1. Dare I say, Brilliant!

  2. Gary

    Top image looks similar to an oocyte (see: Somewhat startling when you contemplate the size differences.

  3. gopher65

    Wowzers. I didn’t know you could take images like that from Earth that weren’t from a professional scope!

  4. Umm… Err… Uhh…


  5. Bob

    So that is how Dr. Manhattan sees the sun…

    Wish I could…

  6. Messier Tidy Upper

    Better than brilliant – its superluminous! 😉 8)

    Awesome, awesome, strange and awesome solar imaging.

    Thanks. :-)

  7. MiSH

    The image belongs in a gallery or museum. It is art.

  8. Bjoern


    I like seeing familiar things in new ways. It jolts me out of complacency. What more can a skeptical scientist ask for?

    Well, then that:
    is still the best “picture” of the sun available…

  9. Minos

    “A million Earths could fit inside the Sun.” Every time I hear that I get Why Does the Sun Shine running through my head. Particularly one live version I used to have:

    “If the sun were hollow, a million Earths would fit inside. But they can’t, because that would be too f****d up!”

  10. Murff

    Worship the Sun!! lol. Those are stunning picture’s, really awe-inspiring!

  11. gia

    Oddly enough the image reminds me of a zygote…

  12. Many fine amateur images can be seen on the Cloudy Nights Solar forum in h-Alpha, CaK and white light. The sun is HUGE and relatively close, so seeing fine detail from the earth can be accomplished with fairly small scopes.

  13. Dang… I thought that was from a NASA observatory. Well done!

  14. I hope Alan appreciates your glowing reports. He certainly has a lot of bright ideas.

  15. My pleasure, Phil….I love Alan’s work. I still can’t believe he gets these shots from his !@&% backyard! Thank heavens he uses his powers for good and not evil (I think)….

  16. rob

    very very very etc nice photo! Alan is talented!

  17. Nigel Depledge
  18. XPT

    Spectacular picture! The level of detail, man!

  19. Amazing photo… wow… 😮

  20. Nicole

    WHOA. I SO have to take up space photography.

  21. His other photos from day are just as amazing:

  22. Evil Eye

    VY Canis Majoris makes our Sun look like a speck of dust. And the Universe makes VY Canis Majoris insignificant.

  23. WOW, that is just …. (NO WORDS). This really makes me think to invest in a relatively small telescope, because this image is much nicer than anything I have done on a professional telescope. (not that I have ever observed the sun, but still …)

  24. A White
  25. Jeff

    ” Our planet is about 13,000 km (8000 miles) in diameter, so that one minor prominence is roughly 50,000 km high. That’s 30,000 miles. And it’s positively dwarfed by the Sun itself. A million Earths could fit inside the Sun.”

    yes, I’ve done for the students since 1988 a simple sunspot activity: get a small telescope , aim on sun and project sun’s photosphere on a screen. (NEVER LOOK AT SUN DIRECTLY, I DON’T EVEN LOOK AT IT WITH A THICK FILTER, THAT’S HOW JITTERY I AM ABOUT THAT) . Then measure the diameter of the solar disk in millimeters, and the size of the spot in millimeters. Take the ratio of these and the number will be a small fraction. Now multiply this small fraction by the number 1,400,000 kilometers (the real diameter of sun) to get the size of the spot in kilometers, and you’ll almost always find this bigger (lot bigger usually) than earth diameter of 13,000 km.

    This blog image is the most amazing of the photosophere and chromosphere I’ve seen. (a) usually the photosphere is puntuctuated by “granulation: bright and darker areas like a mottling appearearance”, but here you can see the reality: 3 dimension views of the convection cells.
    (b) the “spicules” can be seen clearly as a fuzz around the limb like little spikes of gas rising into the chromosphere.

  26. Fredrik

    Is it just me or do the plumes look fake, like they’re generated by a particle system in a video game?

  27. Barbara

    I definitely have that optical illusion you’re talking about. In fact I looked at the sun a little too long and now I’m feeling kinda nauseated. I expect the effect has to do with the complementary colors in the picture and my particular vision anomaly where I have one bookworm eye and one hawk eye. They take turns trying to make things more in focus than they really are. Hurray for spasms of accommodation.

  28. @Astronomovie: Realize that this image was taken with a specialized Hydrogen Alpha scope which while small, are very expensive for their size. An 80mm hAlpha scope is about 3X the cost of an 80mm apochromatic triplet.

    Not trying to discourage you, if you’ve got it, spend it. But most get severe sticker shock when they price solar scopes.

  29. “Spalding” must be on the other side (the dark side?).

  30. Mightypuparoo

    The top picture reminds me of a microscope photo of a virus. This is a very cool picture, stunning really. Thank you for sharing, it keeps me thinking. :)

  31. Hmmm. There was supposed to be a picture of a basketball in my post. I’ll have to figure out why it didn’t show up.

  32. Nice work Alan!
    This is the most exciting new hobby in astronomy folks. There are about 20 or so of us over at cloudy nights. Come on over and let us explain it all to you and get you started…

  33. I thought it was an egg about to be fertilized.

  34. Geert


    And yes, the optical illusion is there for me as well…
    Must be one of those nasty software bugs built in the visual cortex :)

  35. Robert LeClare

    And to think it,s only temporary and will someday be gone……

  36. You can get pics like this with modest equipment from the ground if you are good…really good. Alan is really good.

    @Astronomovie The least expensive H-alpha telescope, the PST, starts at about $500 without a mount. The PST is nice for introductory visual observing, but you need something bigger and with a narrower bandpass to get photos like this. I have a PST and it gives nice views…but there are days I envy the bigger scopes!

    Phil, you need to get yourself a PST so you can do some H-alpha observing…then you would know that the Sun is limb darkened in H-alpha light :)

  37. Charlie

    An idle question for anyone who knows the answer: when you say “A million Earths could fit inside the Sun” does this mean the volume of the sun is one million time the volume of the earth, or that one million spheres the size of the earth could fit in a sphere the size of the sun? I think there is a difference but don’t have the math chops to answer the second part of the question (at least without cracking open a 40-year-old high school geometry book).

    Awesome picture BTW.

  38. The sun is truly an amazing and beautiful object. This perspective cements that opinion even more. Thank you for sharing.

  39. james

    I see the optical illusion. I attribute it to the extremely high contrast. Beautiful picture.

  40. t-storm

    @26 It looks fake because it is fake. The sun doesn’t really exist. It’s really just a really bright lightbulb in the sky, and it’s not one of those compact flourescents either, the sun is old school.

  41. Major Variola (ret)

    Your admission of mistake is more important than anything you wrote. For science, etc.

    Thank you.

  42. Major Variola (ret)

    Guys: the sun is 100x the diameter of earth. That means 100 x 100 x 100 times the volume.
    There’s your millions times.

  43. Major Variola (ret)

    One last small point. When a nuke goes off, its apparent temperature is near that of the sun. But the area subtended by the 5000K surface is much larger than the half-degree of Sol, so you

    Just trying to help with the physicsgrok.

  44. @37. Charlie: a million Earths could fit inside the Sun. About 109 Earths could be placed across the equatorial width of the Sun.

    Here’s a diagram I made up using info I scrounged up on various general-science answer sites:

    I’ve heard it said that the Sun comprises 98% of all the matter in our entire solar system! Not sure how that’s measured exactly, but it sounds impressive.

  45. me

    and there was me thinking it was the wheel of a giant chariot

  46. Kit

    @37. Charlie, I did a (very) rough calcuation for you.

    It would take 1.3 million earths to fill the sun if they were melted down and poured in like a liquid.

    It would take about 220 thousand earths to fill the sun, assuming the earth is in fact a cube of the same diametre.

    So I’m going to take a guess and say the actual answer, for the earth as a solid sphere, is about 300-400 thousand.

  47. Charlie

    @44. J Major – thanks. I decided to query Wolfram Alpha for the vol.sun/ = approx. 1,300,000. I’d like to see the math showing how many BB-earths could fit in the basketball-sun. Maybe I’ll try to work it out but it’s been a while since I’ve done that kind of math.

  48. jick

    @47 Charlie:

    Hexagonal close packing (or face-centered cubic) can utilize about ~74% of available space. (Of course this ignores the boundary of the sun, but since the sun is *pretty big* I think we can ignore it.)

    So you can get 1.3 million * 74% = ~960 thousand earths.

    Pretty close to a million earths, I’d say.

  49. Trish

    My first thought was of a human ovum. Brilliant capture.

  50. mfumbesi
  51. Phobos

    Amazing. Looks like something you’d see under a microscope.

  52. scott

    what would the consistancy of the suns material “feel” or be like…if you could be on the surface, and scoop some up in a sample container, etc…is it vaporous, like a cloud, lightly gaseous like fire..perhaps thicker, with a feel and consistancy like a liquid? forget the heat, the radiaiton, the roiling…does anyone have any thoughts on how it might feel.

  53. Charlotte

    The sun is a miasma of incandescent plasma/The sun’s not simply made out of gas, no, no, no…


  54. AJ in CA

    @53 scott: Hmm… Interesting question. My two cents: That depends where on the sun you are (the outer atmosphere, the visible surface, the core?) The plasma is compressed by gravity more and more toward the core, so it’d act more or less like a gas, but with greater and greater density.

    @54 charlotte: I’m a new TMBG fan now 😀

  55. Laura

    That optical illusion you speak of can probably be attributed to simultaneous contrast and the afterimage effect. It causes a sort of vibration between the orange and blue because they are complements and gives that shrinking effect- I see it, too.

  56. Brian Too

    I’m always impressed by these high quality solar images. We experience the sun as a constant thing. It’s very stable on human timescales. And of course it’s so bright that, without technology, it’s just a blindingly bright disk in the sky.

    Then when we can really look at it, you discover this turbulent, fractal-like quality. It is both stable and chaotic. Chaos at a micro scale but startlingly stable and predictable at the macro level. And of course there is the whole “hidden life of Sol” angle.

    Great stuff.

  57. Laura Brown

    It’s only a 3D composition.

  58. Andrew

    What? The sun is NOT a gas, it’s a plasma. Gas can’t follow magnetic field lines, it’s electrically neutral. Plasma is ionized, thus, the ability to flow along the sun’s magnetic fields. C’mon Phil, get it right.

  59. Wow – Alan’s pics are really getting a lot of (well-deserved) press!!! Awesome!

  60. Prometheus Kane

    The article didn’t say what kind of camera and what type of lenses were used. I wish it did.

  61. Hold On

    Wow great pic.. and thanks for the info about vy canis majoris, that’s incredible too!

  62. jvdh

    sorry, but its just a tennisbal (to me)

  63. Otto Hunt

    The image on Google+, and at (but not at the top of this page) show some bright white spots near the center. What is that?


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