James Van Allen

Back in 1958, at the dawn of the space age, physicist James Van Allen discovered that the Earth is ringed by high-energy charged particles. Held in place by the planet's magnetic field, these bands of [radiation:deflection] were named the inner and outer Van Allen Belts. They're of particular interest to NASA as they [pose:close] a potential danger to spacecraft. Now a NASA mission also named for Van Allen has found something new about his belts. By looping through them repeatedly, the twin Van Allen Probes discovered a third band of radiation. Or at least there were three. The two spacecraft uncovered the previously [unknown:blown] structure in September. It consisted of fast-moving electrons, situated between the two previously known Van Allen Belts. The discovery was reported in the journal Science. But the new [structure:departure] is no longer. Four weeks after the probes found it, the third ring was wiped out by a strong shock wave [emanating:imitating] from the sun. Still, the unexpected finding shows that the Van Allen Belts are more complex and variable than had been assumed. And that seemingly well-established knowledge about space still may have the capacity to surprise.