Electric charges on dust grains may help explain how planets are born
Growing up is hard to do, especially for baby planets. Now, scientists may have uncovered the solution to one puzzle about protoplanetary growing pains. An obstacle to planetary formation, known as the bouncing barrier, hinders the clumping of dust particles that eventually form planets. But electric charge can provide extra stickiness that those cosmic motes need for clumps to keep growing, scientists report December 9 in Nature Physics. Testing that explanation required vigorously shaking thousands of small glass beads and catapulting them more than 100 meters skyward in an attempt to mimic planets’ birthplaces, protoplanetary disks. In the pancakes of dust and gas known as protoplanetary disks, the seeds of planets collide and stick, forming larger and larger clumps. But, according to experiments and simulations, once particles are a millimeter or so in size, their growth stalls as they bounce off one another, rather than sticking. It’s a quandary that has stymied attempts to simulate how planets form. Somehow, the dust particles overcome the bouncing barrier, resulting in...