A year of the Sun, in three minutes
The equinox has been and gone, the evenings are suddenly long, and I am losing my observing hours at a rate of several minutes a night. That is the trade every spring. The Sun gives you warmth and light and takes away the sky.
I have never observed the Sun properly. You need either a certified white-light filter over the front of the telescope or a projection set-up that I do not trust myself to use without someone looking through the finder by accident. Everything I have read on the subject comes down to the same sentence: one mistake and the damage to your eye is permanent. So I leave it alone.
Instead, this NASA clip from the Solar Dynamics Observatory, which photographs the Sun continuously from orbit. It compresses one year into about three minutes, using two frames a day in extreme ultraviolet:
What to watch for:
- The bright knots are active regions, the areas above sunspots where the magnetic field is tangled. In ultraviolet they glow rather than looking dark.
- The Sun's rotation is obvious once you notice it: features appear at one edge, cross the disc in about two weeks and vanish over the other.
- Dark patches near the poles and sometimes in the middle are coronal holes, where the field opens out into space and the solar wind streams away.
- Watch one edge for a minute or so and you will see loops lifting off the limb. Those are each the size of several Earths.
The year in this clip is from an earlier, quieter stretch of the Sun's eleven-year cycle. The Sun at the moment is said to be near the busy end of the cycle, so a clip from this year would presumably be more crowded with bright regions.
I find it hard to watch without thinking about the starter on the kitchen shelf. Both are churning away at their own pace, both look static if you check once, and both only reveal what they are doing when somebody puts them on a time-lapse.