The Sun is a giant ball of gas and is in constant motion. Prominences are structures of gas suspended over the Sun that are held in place by opposing magnetic fields. Looking through a solar filter with an H-alpha bandwidth, you can view prominences off the limb. These structures are called filaments when you see them scattered across the solar disk itself.
There are two general categories of prominences: active and quiescent (quiet). “Active” would include solar flares, sprays, surges and loops. “Quiescent” includes your typical day-to-day views of prominences that move slowly. A solar flare (not to be confused with a coronal mass ejection) can occur within a matter of seconds whereas an erupting quiescent prominence may occur over the span of a few hours.
The temperature of a quiescent prominence is ~10,000 degree C and can live for months. A typical solar observing session may show several prominences of various shapes and sizes scattered across the limb. At first glance they appear…well…quiet and unchanging. A quick glance an hour later and you think to yourself that perhaps it changed slightly, but you’re just not sure. If you’ve ever tried to sketch one, though, you may have noticed that after several minutes, the shape of the prominence in your sketch looks a little off. You may even reach for an eraser to correct it. As you continue your sketch, your frustration builds up because you’ve noticed that you’ve done it again.
The problem isn’t with your sketching ability but rather because the prominence itself is changing that rapidly. Like a formation of clouds on a calm day, the changes are subtle, but they’re most definitely there. If you work on increasing your sketching speed for prominences, you’ll overcome that problem.
This sketch sequence shows the changes of a prominence over the course of 3.5 hrs. I’ve enjoyed recording such sequences over the span of several days, sometimes weeks when I include the disk features as well.
Alan Friedman, a fellow solar observer and amazing imager, was very kind to create an animation of this sketch sequence for me.
Observation report from 2007 June 09:
2007 06 09, 1500-1945 UT – PCW Memorial Observatory, Ohio – Erika Rix
Internally Double stacked Maxscope 60mm with 8mm TV Plossl, LXD75
Seeing above average with only a few moments of quivering, transparency above average, temps 66.9 °F / 19.4 °C to 75.9 °F / 24.4 °C over course of observation, winds from North at 6.9 mph / 11.1 km/h, clear, humidity starting at 49% going down to 31%.
This was to be my first solar session in the new observatory. It will be strange not having the LXD75 in my living room anymore, but the most loved Maxscope will still remain in the house with me when I’m not observing. Riser and Buttercup (the two younger dogs) kept me company during the session today. Buttercup was the guarding the door (I’m sure anyone could have bribed her a dog cookie and she would have happily let them in) and Riser found a shady spot behind my truss dob.
I started off with putting the Thousand Oaks white light filter on the LX200. Now that the LX200 has its own pier so that I don’t have to tear down and set it up, I finally had a chance for first light on this filter since we bought the scope used a few years back. Wouldn’t you know it wouldn’t seat properly on the OTO because of the brackets for mounting the ED80 on the scope? I’ll have to see about fixing that situation soon. In the mean time, I can always resort back to the ETX70.
On to the fun part, now…the Maxscope views.
The flare activity this morning had pretty much subsided by the time my session took place. I was disappointed, but AR0960 was still showy with AR0959 accessorizing it nicely. There was thin plage marking 959 as well as plage just East of the center of the disk, and also very thinly following the path of a long slender filament just inside the Eastern limb. Add the remarkable plage details in AR0960 to that, and you have a straight line of interrupted plage going from East to West.
The two spots within 960 were easy to spot as black dots. There was a third dot just North of them that I first thought was another spot to that region. But I’m pretty sure it was a little piece of filament having compared my sketches to other images afterward.
When tuning, I could easily pick out several other filaments across the disk even though they were very slender and short, almost like little crooked crosshairs of an eyepiece. There were five definite prominences with a few little hints of others on the limb. The huge prominence that was evident on the NW limb earlier this morning was no longer there that I could see. However, the “pick of my pleasure” prominence was the presence of an “m” shaped faint one on the NE limb. And this, my friends, became the start of a three and a half hour project for me today. It made no matter that I had lots of chores to do. Astronomy comes first…at least today.
The series for this one prom was rendered in two sessions. An hour with 1 minute intervals, an hour and a half break so that I could at least get the riding mower part of the grass cutting done, and then another hour session with 10 minute intervals again. I would have loved to spend the entire day doing this, but I was starting to get sunburn on my farmer’s tan legs and feet that today sported sandals instead of sneakers. Nevertheless, perhaps 12 sketches of the same prominence were enough to show how dynamic the Sun is over such a short period of time.
Sketches were done with black Strathmore paper and colored Conte’ crayons for the full disk, white Conte’ for the prominence sequence.
Posted in Solar Observations, Solar Observations 2007
Tags: animations, H-alpha, prominence sequence, solar, solar sketches, Sun
PCW Memorial Observatory - Erika Rix 
