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It's weird I wrote some sun materials in the past, for a game, and I ended up roughly with that. What I based myself on was a sci-fi movie (can't remember), and

by keyle 7y ago

It's weird I wrote some sun materials in the past, for a game, and I ended up roughly with that. What I based myself on was a sci-fi movie (can't remember), and they had it right. Can't really figure out why it looks that way though, anyone care to explain why it rises and drops like that? Is there anything like currents, or it's a straight up and down? Does the sun rotate at all or it's 'static' from our perspective? (I imagine it's rotating with the stars within our galaxy)

oliverhopcrof 7y ago
I know next to nothing about the sun but I think the article implies that it’s because of convection currents—closer to the center, plasma heats up and expands, rises, cools off, and falls back in. The picture looks vaguely like a Voronoi diagram too, which sort of fits as the plasma has to spread out of its own hot plume before sinking.
- phodo 7y ago
  I had a similar comment about voronoi. Nature and science are beautiful.
- chongli 7y ago
  Close. The Sun is not a fully convective star. Convection only occurs in the outer 30% or so. The inner part is called the radiation zone [1] and it is here that energy from fusion in the core makes its way out by radiative transfer as well as conduction. This is a very slow process compared to convection, taking more than 170,000 years for the photos produced by fusion to reach the convection zone. [1] https://en.wikipedia.org/wiki/Radiation_zone https://en.wikipedia.org/wiki/Radiation_zone
  - oliverhopcrof 7y ago
    Wouldn’t we be observing the outer 30% (or 1%) though? From the diagram on the page you linked it seems that the granules in the photo exist in the photosphere, where convection is the dominant mode of energy transfer. That said, none of the conduction could happen without radiation further inside.
    - chongli 7y ago
      Yeah, we’re seeing the convection from the outer 30%, bubbling up on the surface of the photosphere. All of the fusion takes place down in the core though. It’s very difficult to fuse hydrogen and so it can only occur at the extreme pressures in the middle of the sun.
samplatt 7y ago
>a sci-fi movie (can't remember) Sunshine, perhaps? https://en.wikipedia.org/wiki/Sunshine_(2007_film) https://en.wikipedia.org/wiki/Sunshine_(2007_film) Brilliant, brilliant film. The premise is shonky as they come but it's obvious that the film itself has little to do with the premise. Awesome acting, literally-awesome SFX (their ability to give the sun so much weight is amazing, you really get a sense of an immortal unstoppable force), and a message that's neither shallow nor deep but prompts some self-reflection in ways you don't expect.
- hossbeast 7y ago
  But at one point, they jump between two airlocks, and while in space for 10 seconds they become completely covered in ice and freeze to death.
  - andrewingram 7y ago
    I vaguely recall something about the making of the movie where they acknowledge that this wouldn't happen, but it was done because that's what the audience expects.
    - nkrisc 7y ago
      I always thought that would be a good opportunity to teach people, but I guess if you're in it to make money it makes sense to just pander to what audiences expect.
      - ssully 7y ago
        It's not about pandering or making money (did people go to the movie because they heard there was a scene where a guy freezes in space?????), it is entertainment.
        nkrisc 7y ago
        It's absolutely about making money. Most movies are made primarily to make money. And the way to make money is to make it entertaining. Is it less entertaining if it's more realistic? In this particular example the answer seems to be, "yes."
SCAQTony 7y ago
"[...] The gasses and plasma near the sun’s equator rotate around the sun’s axis every 25 days. As you move towards the sun’s poles, the rotation speed slows. Near the north and south poles, the sun rotates once every 36 days. That means the sun’s poles take 11 more days to rotate around the sun’s axis than its equator. The differing speeds of rotation is called differential rotation, meaning different parts rotate at different speeds. In fact, scientists divide the sun into four general sections and each section spins at a different speed.[...]" https://nineplanets.org/questions/does-the-sun-rotate/ https://nineplanets.org/questions/does-the-sun-rotate/
cbracken 7y ago
> Does the sun rotate at all or it's 'static' from our perspective? It does, though not being a rigid body, the rate of rotation is a function of latitude. Near the equator, the period of rotation is ~24 days. As you near the poles, the period is closer to 30-35 days. A means of measuring these rates available to backyard astronomers is through measuring the positions of sunspots over time. [1] [1] Please don't look at the sun through a telescope or really at all without knowing what you're doing and taking appropriate precautions: https://www.youtube.com/watch?v=R9cMXCemoJI https://www.youtube.com/watch?v=R9cMXCemoJI
SiempreViernes 7y ago
Not very weird, since the BBC video only illustrates resolution that's been available for the last decades. Here's a really old picture that is at essentially the same scale as what the BBC decided to show, but made in 1997: https://en.wikipedia.org/wiki/Swedish_Vacuum_Solar_Telescope#/media/File:Granules2.jpg https://en.wikipedia.org/wiki/Swedish_Vacuum_Solar_Telescope...
Sharlin 7y ago
It's convection cells, not unlike water boiling in a kettle, the atmospheric circulation that gives us weather, or the ever-so-slow churning of solid rock in Earth's mantle that gives rise to volcanism and plate tectonics. The timescales are very different, though.

by keyle 7y ago

oliverhopcrof 7y ago

I know next to nothing about the sun but I think the article implies that it’s because of convection currents—closer to the center, plasma heats up and expands, rises, cools off, and falls back in. The picture looks vaguely like a Voronoi diagram too, which sort of fits as the plasma has to spread out of its own hot plume before sinking.

phodo 7y ago
I had a similar comment about voronoi. Nature and science are beautiful.
chongli 7y ago
Close. The Sun is not a fully convective star. Convection only occurs in the outer 30% or so. The inner part is called the radiation zone [1] and it is here that energy from fusion in the core makes its way out by radiative transfer as well as conduction. This is a very slow process compared to convection, taking more than 170,000 years for the photos produced by fusion to reach the convection zone. [1] https://en.wikipedia.org/wiki/Radiation_zone https://en.wikipedia.org/wiki/Radiation_zone
- oliverhopcrof 7y ago
  Wouldn’t we be observing the outer 30% (or 1%) though? From the diagram on the page you linked it seems that the granules in the photo exist in the photosphere, where convection is the dominant mode of energy transfer. That said, none of the conduction could happen without radiation further inside.
  - chongli 7y ago
    Yeah, we’re seeing the convection from the outer 30%, bubbling up on the surface of the photosphere. All of the fusion takes place down in the core though. It’s very difficult to fuse hydrogen and so it can only occur at the extreme pressures in the middle of the sun.

samplatt 7y ago

>a sci-fi movie (can't remember) Sunshine, perhaps? https://en.wikipedia.org/wiki/Sunshine_(2007_film) https://en.wikipedia.org/wiki/Sunshine_(2007_film) Brilliant, brilliant film. The premise is shonky as they come but it's obvious that the film itself has little to do with the premise. Awesome acting, literally-awesome SFX (their ability to give the sun so much weight is amazing, you really get a sense of an immortal unstoppable force), and a message that's neither shallow nor deep but prompts some self-reflection in ways you don't expect.

hossbeast 7y ago
But at one point, they jump between two airlocks, and while in space for 10 seconds they become completely covered in ice and freeze to death.
- andrewingram 7y ago
  I vaguely recall something about the making of the movie where they acknowledge that this wouldn't happen, but it was done because that's what the audience expects.
  - nkrisc 7y ago
    I always thought that would be a good opportunity to teach people, but I guess if you're in it to make money it makes sense to just pander to what audiences expect.
    - ssully 7y ago
      It's not about pandering or making money (did people go to the movie because they heard there was a scene where a guy freezes in space?????), it is entertainment.
      - nkrisc 7y ago
        It's absolutely about making money. Most movies are made primarily to make money. And the way to make money is to make it entertaining. Is it less entertaining if it's more realistic? In this particular example the answer seems to be, "yes."

SCAQTony 7y ago

"[...] The gasses and plasma near the sun’s equator rotate around the sun’s axis every 25 days. As you move towards the sun’s poles, the rotation speed slows. Near the north and south poles, the sun rotates once every 36 days. That means the sun’s poles take 11 more days to rotate around the sun’s axis than its equator. The differing speeds of rotation is called differential rotation, meaning different parts rotate at different speeds. In fact, scientists divide the sun into four general sections and each section spins at a different speed.[...]" https://nineplanets.org/questions/does-the-sun-rotate/ https://nineplanets.org/questions/does-the-sun-rotate/

cbracken 7y ago

> Does the sun rotate at all or it's 'static' from our perspective? It does, though not being a rigid body, the rate of rotation is a function of latitude. Near the equator, the period of rotation is ~24 days. As you near the poles, the period is closer to 30-35 days. A means of measuring these rates available to backyard astronomers is through measuring the positions of sunspots over time. [1] [1] Please don't look at the sun through a telescope or really at all without knowing what you're doing and taking appropriate precautions: https://www.youtube.com/watch?v=R9cMXCemoJI https://www.youtube.com/watch?v=R9cMXCemoJI

SiempreViernes 7y ago

Not very weird, since the BBC video only illustrates resolution that's been available for the last decades. Here's a really old picture that is at essentially the same scale as what the BBC decided to show, but made in 1997: https://en.wikipedia.org/wiki/Swedish_Vacuum_Solar_Telescope#/media/File:Granules2.jpg https://en.wikipedia.org/wiki/Swedish_Vacuum_Solar_Telescope...

Sharlin 7y ago

It's convection cells, not unlike water boiling in a kettle, the atmospheric circulation that gives us weather, or the ever-so-slow churning of solid rock in Earth's mantle that gives rise to volcanism and plate tectonics. The timescales are very different, though.