Lois & Clark Forums Forums General Discussion Off Topic Fantastic picture of the solar corona

Here is a picture of a solar eclipse, although that is not the picture I refer to in the topic heading:



I suppose that the black round thing that makes the Sun look black in this picture is the Moon. Surrounding the face of the Moon (which is covering the face of the Sun) is the solar corona.

Normally the Moon isn't positioned right in front of the Sun from us Earthlings' point of view, and then the Sun looks like this:



Okay, I'm just joking with you! And the guy in the picture is joking too, as he is positioning his hands relatively to the position of the Sun and the location to the camera taking the picture so that it look like he is holding the Sun in his hands! Well, hmmm. He isn't.

But you may notice that in this picture we don't see the corona. Instead the Sun looks like a brightly shining round disk. The Sun appears to have a very sharp boundary. This brightly shining sharply bounded round disk of the Sun is the outermost brightly shining layer of it, and it is called the photosphere.



The structure of the Sun. Okay, maybe the photosphere isn't the very outermost brightly shining layer of the Sun, because there is something called the chromosphere too. Big deal. The chromosphere is thin, and you can't tell the difference between the photosphere and the chromosphere when you look at the Sun through a proper solar telesope. (Don't stare at the Sun with the naked eye, and never look at the Sun thorugh a pair of binoculars or a telescope unless you know that you have a proper solar filter!!!)

Back to the photosphere. For all intents and purposes the photosphere is the outermost clearly visible layer of the Sun, and its temperature is a little less than 6,000 degrees Celsius. Have fun figuring out how much that is in Fahrenheit.

The reason why the Sun appears to have this sharp boundary is that for some reason that I can't explain, this is the "level of the Sun" where it becomes transparent to photons. Huh?



Photons. Oh well.

But don't panic! Photons are "light particles", and they are generated in the scorching hot interior of the Sun, where the temperature is around 15 million degrees Celsius. But the photons which are created there are gamma rays, extremely energetic and dangerous photons.

Gamma rays - watch out!

Fortunately for us, the Sun is all but opaque to the gamma ray photons. So as the super-energetic photons try to leave the Sun, they keep bouncing around in there! Indeed, if I remember correctly, the average photon generated inside the Sun takes a hundred thousand years to make it to the photosphere, where the bouncing finally stops and the photon is free to escape (and hit us)! Wowzers! And during all those years of bouncing around, the photons keep losing energy. That's a good thing for us, let me tell you. After bouncing around as if they were in a pin ball machine the photons have been "whittled down" to the energy level that we are used to from sunlight! Imagine that it takes a hundred thousand years of zipping around inside the Sun to cool down the photons to the proper life-friendly energy level!

Well, that was the photosphere. Outside the photosphere, however, you find the corona. Normally the corona is invisible, but it can be seen during solar eclipses. Fascinatingly, the corona is extremely hot, about a million degrees Celsius, if I remember correctly. It is also quite thin, fortunately. Astronomers believe that the corona is heated by strong magnetic activity on the photosphere.

Here you can find an absolutely amazing image of the corona, the thin colorless gas heated by strong magnetic fields so that it is "lining up" along magnetic lines extending from the Sun. Also note the solar protuberances glowing pink from hydrogen alpha emission. The protuberances can be compared with the surface of boiling water. (Hmmm, I guess that the "boiling water surface" is the chromosphere!) And the corona can perhaps be compared with the water vapor leaving the boiling water.

Oh, and just in case you were wondering, the dark mottled surface that is covering the Sun is our dear old Moon, of course!

ann

Thanks for posting this! I always learn something from your posts.

Thanks for sharing those amazing photographs, along with the science lesson. :-) I already knew some of it, but there was a lot that was new to me, too.

cheers,
Lynn