Comets & the Solar Wind
- Early evidence that the sun might be continuously expelling plasma at a high speed came from observations of the dual tails of comets.
- One tail, made of dust slowly driven away from the comet by solar radiation, has an orientation that is tilted to the anti-sun (radial) direction by the comet's own orbital motion.
- A second tail comes from cometary ions picked by the solar wind. It's more radial orientation implies that the radial outflow of the solar wind must be substantially faster than the comet's orbital speed.