The Sun is Spectacular Today in H-Alpha (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Mon, 07 Mar 2022

The Sun is Spectacular Today in H-Alpha

[Sun in h-alpha on 2222-03-07] A couple of years ago, Dave and I acquired an H-alpha solar scope.

Neither of us had been much of a solar observer. We'd only had white-light filters: filters you put over the front of a regular telescope to block out most of the sun's light so you can see sunspots.

H-alpha filters are a whole different beast: you can see prominences, those huge arcs of fire that reach out into space for tens of thousands of miles, many times the size of the Earth. And you can also see all sorts of interesting flares and granulation on the surface of the sun, something only barely hinted at in white-light images.

Except ... not so much. When we acquired the scope (sadly, we bought it from the estate of a long-time friend and astronomy mentor, "Crazy Ed" Erbeck), we soon learned that not only was the sun at solar minimum, but it was the minimost of minima, the quietest the sun had been in many years. And that persisted for years, with nothing more than a tiny blip visible now and then.

But solar minimum doesn't last forever, and in the last few months, the sun has started erupting spectacularly. Perhaps you've read about some of the recent radio disturbances and low-latitude aurorae recently (alas, none of the auroral activity was visible down here at 36° north).

A week or two ago, some of the science news sites described a particularly huge record-breaking prominence, and we realized we needed to start taking out the solar scope regularly. So now it sits by the dining room table, and gets set up on the patio every day that clouds don't interfere. (One nice thing about solar scopes is that they don't need to be large. Even a small scope, like this 40mm Coronado PST, can show plenty of detail while being super-easy to set up.)

We missed that record-breaking prominence, but we've seen some nice smaller ones since then, and this morning there's one spectacular one reaching far out above the limb.

I wanted to let people know about it, and thought I'd look for a "live" H-alpha solar image I could point to — but weirdly, I couldn't find one. There are a few solar observatories that offer a live H-alpha view, but none of them show anywhere near the detail I'm seeing through this tiny 40mm scope, and none of them show prominences at all. Hard to believe! If you know of a good H-alpha live website, please let me know in the comments, or send me email and I'll add a link here.

Since I couldn't find a website, I tried to capture the PST's image afocally: I held a little digital camera to the eyepiece and made a bunch of shots at different exposure compensation settings, then combined the two best ones in GIMP. It still didn't quite manage to capture the big prominence — you can see it at about 2:30 in the photo, but there's a lot more to it that didn't come through in the image.

And in the 15 minutes I've been writing this plus the 15 minutes I spent GIMPing the image, the prominence has changed completely. When I first set up the scope, at about 10:30am MST, it was a long unconnected arm reaching out into space. Now it's a huge loop arcing back to the sun. I had no idea something six or eight times the size of the Earth could change that fast. (I'm guessing the gas making up the prominence isn't moving that fast, but rather, the Sun's magnetic field is affecting which parts of the gas we see through the H-alpha filter.)

So I guess I'll leave the scope set up all day and watch as it changes. If you're local, drop by and take a look!

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[ 12:00 Mar 07, 2022    More science/astro | permalink to this entry | ]

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