The spacecraft are still feeling the sun billions of miles from home.
The missions that humankind has sent farthest into space, a pair of NASA spacecraft called the Voyagers, are billions of miles from Earth. The last time one of them took a picture of its surroundings was in 1990, after flying by Jupiter, Saturn, Neptune, and Uranus on its way to interstellar space, the mysterious expanse between stars. This far beyond the planets, there’s not much to see.
But there are some things to feel, in the sense that a spacefaring machine can feel something. Even this far out, the sun can still make its presence known.
A team of scientists has detected sudden bursts of cosmic rays around the Voyagers. The bursts, they report, are caused by shock waves emanating from solar eruptions that spew particles out at a million miles an hour. The shock waves take more than a year to reach the Voyagers, but when they do, they excite cosmic-ray electrons nearby. Scientists have observed similar phenomena closer to home, around Earth and our planetary neighbors, but never in interstellar space.