From a press release:
NASA researchers using the Solar and Heliospheric Observatory (SOHO) spacecraft have developed a method of seeing through the sun to the star’s far side. The sun’s far side faces away from the Earth, so it is not directly observable by traditional techniques.
Only it’s not seeing, it’s hearing.
The sun is filled with many kinds of sound waves caused by the convective (boiling) motion of gas in its surface layers. The far side imaging method compares the sound waves that emanate from each small region on the far side with what was expected to arrive at that small region from waves that originated on the front side. An active region reveals itself because its strong magnetic fields speed up the sound waves. The difference becomes evident when sound waves originating from the front side and from the back side get out of step with one another.
This is so mind-bogglingly cool. Not just because hearing sunspots on the far side can tell us if we have magnetic storms coming in two weeks. (It takes the sun 27 days to revolve) Not just because it can allow for better planning of all sorts of things that are disrupted by solar flares and the energy they release.
No, though all that is great. It’s just, all by itself, really, truly, mind-bogglingly cool.