Bad Astronomy

One solar piece of flare

The Sun is displaying its individuality – I guess the manager at Chochkies finally got through to it – by showing a nice little flare the other day:

This image, taken by the STEREO spacecraft (for Solar Terrestrial Relations Observatory), shows the Sun in the far ultraviolet, almost at X-ray energies. The bright flare is on the left. The slightly tilted elongated diamond is not real; it’s what happens when an electronic detector gets flooded with light. Detectors like this convert photons of light into electrons, and if too many photons hit it, the electrons leak out and “bloom” into nearby pixels.

Flares happen when the magnetic field lines of the Sun get tangled up. A huge amount of energy is stored in those lines! If the magnetic field gets too entangled, they can suddenly reconnect and release that energy. In my book, I make the analogy to a bunch of bed spring coils all under tension and thrown into a bag. If one snaps back, it hits the others which then snap, and you get a very quick and very violent release of energy. For the Sun, that means a solar flare is released. The one shown here is little, but big ones can release as much as 10% of the Sun’s total energy! They roar out, vast and powerful across the electromagnetic spectrum, from radio waves to gamma rays, and unleash a flood of subatomic particles as well.

If you look to the right of the flare, you’ll see some arcs extending up from the Sun’s surface. Those are also loops of magnetic energy, and a little time after this image was taken they too snapped, releasing a coronal mass ejection; it’s spread out more than a flare, so it’s less intense, but CMEs can blast out huge amounts of energy as well.

Images like this, and more observations by STEREO, help astronomers understand our nearest star better. And this isn’t just academic knowledge: flares and CMEs can damage or even destroy satellites, which represent billions of dollars of assets. The government and private companies take this threat very seriously indeed, of course. Just imagine the number of TPS reports they’d have to fill out!

Image credit: NASA, STEREO