Cloudy Crossing

The space around our solar system is cloudy. Astronomers have mapped 15 individual clouds within a few hundred light-years. The clouds are moving in different directions, and they have different mixtures of ingredients. Some of those ingredients were forged by exploding stars. Over the past few years, scientists have used one of those ingredients to trace the solar system’s path through the Local Interstellar Cloud. It’s about 30 light-years across, and we’re close to its edge – perhaps in the transition zone with the next cloud. The scientists have looked at a radioactive form of iron that’s produced when a massive star explodes as a supernova. The explosion scatters the atoms, creating clouds of debris – including iron-rich dust grains. As Earth flies through a cloud, it sweeps up some of the dust, which falls to the surface. The scientists have found the iron in sediments on the bottom of the ocean, and in fresh snow in Antarctica. And recently, they found it in layers of ice deposited 40,000 to 80,000 years ago, also in the Antarctic. Those samples fell to Earth before the others did. And they have lower amounts of the radioactive iron. That could mean that Earth was just entering the Local Cloud during that period. The amount of iron went up as we passed deeper into the cloud. Now, the amount is going down again – perhaps heralding the solar system’s exit from the Local Cloud. Script by Damond Benningfield