View Full Version : Can Someone Explain This Close-up Of The Sun?

2009-Mar-31, 10:03 AM
Initially this picture is supposed to show some fantastically intense magnetic fields, hence the big white arrow pointing to the flaming valleys, which is not what I'm asking about. It's everything else in the picture. I don't even know what I'm looking at to look it up.

Such as why does it resemble a log burning down to embers?

What are the lumps called?

What are the spaces between the lumps called?

Why lumps at all? (Oh I know, if you tell me what they're called I'll look them up myself, I can't imagine it's not well known and extensively written about.)

Is there an overlaying layer covering everything other than the corona, like a cornea over an iris? Or are the lumps sticking up like bubbles in a boiling pot?

grant hutchison
2009-Mar-31, 10:34 AM
The bright lumps are solar granules or solar granulations, if I'm understanding the picture correctly: they're short-lived convection cells, rising in the middle and descending at the edges. I'm not aware of the darker "spaces" having names, since they're just the edges of neighbouring granules.
The bright thing your arrow is pointing at is called a facula.

Grant Hutchison

2009-Mar-31, 10:37 AM
You might try Solar Granulation as a search phrase.

Basically hotter gasses well up in the center of these little convection areas, and cool off as the gas slides away from the top of the welling up. It gets to a place where it meets flowing gas from a neighboring well-up, and the two flows merge and fall to be reheated.

The shape should somewhat remind you of a surface where many soap bubbles meet.

The false color of the picture helps give it that burning embers look. The Sun isn't nearly that red.

Post edit: I see Grant beat me to it.

Jeff Root
2009-Mar-31, 12:45 PM
The image was probably made in a single wavelength of light or in a
short range of wavelenths. Perhaps hydrogen alpha? It needs to be
in a part of the spectrum where the contrast in brightness between
the slightly hotter gases in the granules and the slightly cooler gases
between granules is significant.

As far as I know, the granules are in the photosphere. That is, from
the top of the brightest part of the visible atmosphere down to the
depth where you can't see down any farther. That is a depth of about
300-500 km. The vast majority of the light we see comes directly from
that layer. Light emitted below that layer generally gets absorbed again
at least once before it finally escapes. Light emitted above that layer
is mostly less bright, because the top of the photosphere is where the
gas density drops off so much that there just isn't enough of it to put
out much light. Faculae are exceptions, where magnetic fields push
ions around to make them more energetic than the surrounding gas.

-- Jeff, in Minneapolis