Super hi-res sunspot

By Phil Plait | August 4, 2012 7:00 am

On August 1, astrophotographer Bart Declercq went outside to get some shots of our nearest star. He used a 30 centimeter (12") telescope, two filters, and a pretty nice camera, he took several thousand frames of video of the Sun. Using a technique that allows combining the frames to get the highest resolution image – and then using a further technique called deconvolution to sharpen it a bit more – he was able to create this tremendous picture of a sunspot:

[Click to ensolarnate and get the 3000 x 2000 pixel hi-res version; this picture displayed here is only one part of a much larger image!]

Wow! This sunspot is officially called Active Region 1532, and is still visible on the Sun’s surface. The detail you can see here is amazing; the spot’s umbra (the dark region) is obvious enough, but the amount of small-scale features in the penumbra (the lighter outer region) is incredible. Surrounding the spot are granules; the pebbly-looking structures which are actually huge convection cells on the Sun. Hot plasma (gas where its atoms are stripped of one or more electrons) from inside the Sun rises to the surface, cools, and sinks back down. Granules are the tops of these convection cells.

Sunspots are where the Sun’s fiercely complex magnetic field breaks through the surface, looping outward and back down, beginning and ending in the spots. These loops of magnetism tend to suppress convection. The plasma cools but cannot sink down. The brightness with which the plasma glows depends on its temperature, so the cooler plasma in the spot appears dark against the hotter material around it.

The scale of all this is hard to grasp. A quick measurement on the image indicates that the spot is about 20,000 kilometers (12,000 miles) across… in other words, just the spot’s umbra alone is roughly the same size as the Earth!

It’s easy to forget just how mighty the Sun is, but pictures like this really slam it home. The Sun is a star, 1.4 million kilometers across, 330,000 times as massive as the Earth, and a complex, amazing, and wondrous place.

Image credit: Bart Declercq


Related Posts:

- Close-up of a solar monster
- What a dramatic sunspot!
- Scientists see sunspots forming 60,000 km below the Sun’s surface!
- A computer’s spot in the Sun

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Bart Declercq, Sun, sunspot

Comments (13)

  1. Tara Li

    I have to wonder…

    What’s the theoretical limit to sharpness for this technique? It sounds somewhat like a poor man’s approach to adaptive optics. Using this technique, is it possible to get better resolution than the theoretical maximum resolution based on standard optical physics? For solar imaging – do the granules and such change slowly enough for this to be really valid?

  2. Assuming he’s shooting 30 frames per second video, it would only take a couple of seconds to get thousands of images to stack. Since each one of those granules is about the size of Texas (no offense, granules), I doubt there’d be much change over the course of the imaging.

    The question I have is, are we seeing depth when we look “down” into the spot? It looks like we’re seeing a slice right through the layer of convection…seeing the granules from the side.

    EDIT: that would be me, kuhniGGet, not kuhninnet. Darn iPad….

  3. @Tara : yes, “lucky imaging” as the technique is called could be seen as a poor man’s adaptive optics, and no, this technique cannot get better results than optical physics allow – the diffraction limit applies so the smallest detail a 12″ telescope can record remains around 0.4-0.5″.
    But it does allow us to somewhat defeat atmospheric turbulence, which for almost any practical telescope is the main limiting factor.

    It’s far from perfect, and getting this kind of result does require a pretty calm atmosphere, I can’t pull of images like these every day – although in some parts of the world that is possible.

    Yes, the granules change quite rapidly, but for this technique, I can record up to about 5 minutes before the changes start blurring them – two images taken 10 minutes apart can show quite noticeable changes and in fact my next project is to make a large number of consecutive recordings, and convert them into a video of the boiling sun.

  4. Becky in Atlanta

    The sun better have that looked at. It has asymmetry, an uneven border, variations in color AND it’s larger than a pencil eraser.

    (Sorry…I couldn’t stop myself.)

  5. Klay

    Its kind of surprising how similar this shot looks like a magnification of regular skin cells. All the slightly darker lines almost look like cell membranes, though I’m just assuming those are slight temperature variations.

  6. Grains!! in the surface of the sun. Wonder if there are any applications for metallographic principles in astronomy.

  7. Tara Li
  8. @Bart – Thank you for your time, talent, and dedication to achieving such spectacular results. I look forward to seeing your ‘boiling sun’ video.

  9. MadScientist

    @Greg#6: more like waves rather than grains (and with the right post-processing you can even have amber waves of grain), but ‘granular’ is commonly used to describe the appearance. Look up ‘helioseismology’.

    Is there anyone out there who’s tracked a persistent sunspot group from limb to limb (and preferably a group near the sun’s equator)? Daily shots showing the rotation of the sun (and the tiny contribution of the revolution of the earth) are pretty neat.

  10. Charles Gaunce

    Isn’t the diameter of the earth roughly equal to 8000 miles?

  11. Regner Trampedach

    Bart Declercq @ 3: Thanks for a beautiful picture of both sunspots and granulation. The quality can measure up to the best professional scopes! Well done!
    MadScientist @ 9: I am afraid you are not quite right there. What you see there on the surface of the Sun is not waves. There are waves too, and looking up ‘helioseismology’ is always a good idea. But the waves are pretty hard to see, since they have small amplitude – easiest to see in Doppler (velocity) movies, but still very hard as there are thousands of (standing) modes superimposed on each other. You might be thinking of the noisy looking MDI images of the Sun. It can look like barely resolved granulation, but is in fact highly unresolved, with 5-8 granules per pixel. With MDI the granulations is lost, so you can see the waves – some are on very small scales. There is nothing wavy about granulation.
    Granulation is what convection turns into at a sharp cooling surface, like the solar photosphere. Each cell has smooth warm upflowing plasma at the center, that cools at the surface, turns over and forms the cooler, turbulent downdrafts in the intergranular lanes. We see the granules at about 6400 K and the integranular lanes at 6000K. But you actually see deeper into the integranular lanes because of atomic physics: The plasma gets much more opaque at higher temperatures, so we can’t see nearly as deep in the granules as in the intergranular lanes (about 57km = 36mi difference).
    Sorry for the long explanation – I actually run 3D simulations of these guys :-)
    Cheers, Regner

  12. cosmogeist

    Hard to fathom each one of those ‘cells’ is roughly the size of a continent

  13. Ed

    The penumbra looks like it could have been made from the brushstrokes of a Van Gogh painting. A “starry night” indeed. Or perhaps a sunflower analogy is more appropriate? Nice coincidence…or is it a painter’s presience? Bom bom BOM!

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