Solar H-alpha

(all photos by John Mahony, except the last)

This photo shows a sunspot region with some prominences on the horizon.  Note the bright areas around the spots.  Because of this the sun is in fact usually slightly brighter overall when there are many sunspots.  Prominences generally follow magnetic field lines that extend above the surface, which accounts for the arches and bridges frequently seen.


These photos show more prominences.  This material can leave the surface, as in the second and sixth pictures.  Large outbursts, known as flares or coronal mass ejections, can fling material to the earth, causing auroras when the material interacts with the earth's upper atmosphere.

This image was taken with a CCD camera, which captures a very wide range of brightness.  So much so, in fact, that I had to process different parts differently to get it to show well on a computer monitor.  At the very center is a dark sunspot and its surrounding dark penumbra.  This was processed lighter than the surrounding area or it would have been just one big black spot.  The rest of the center vertical strip shows the turbulent region surrounding the spot.  The surrounding strips show normal solar surface with a "rice grain" texture of light and dark regions- each "grain" is a convection cell.  The right strip of these two was processed lighter since it is near the edge of the sun, which normally appears darker than the rest of the sun.  The far right strip was processed even lighter to show the thin "atmosphere" layer at the surface.  The inset in the right strip was processed brighter yet to show a prominence.  It appears detached from the surface, but this is due only to the great difference in processing.  In fact, all parts of this image are positioned exactly as in the original single image.

Here's the same image, processed more evenly, with color added in Photoshop.


Prominences form in long ridges.  Seen against the surface, they form dark snake-like features.


This image was taken by Buck Harley, using a Baader white-light filter on his 7" refractor, which he later donated to PGO.