A Good Week for Planet Formation
Caleb Scharf: Lots of the details have proven to be awfully tough to figure out. For instance, it’s still unclear how solid material agglomerates into planet-sized pieces. It has been thought that a lot of this process could be hierarchical, starting with tiny dust grains sticking together and building bigger and bigger bits that themselves collide and merge. But it turns out that might not be the sole route. Other options include processes that effectively skip the middle-stages, taking small pieces (dust or pebble-sized material) and having those come together en masse — drawn and dragged into newly-formed atmospheres for instance. And there is uncertainty about the degree to which rocky material crashes around in proto-planetary systems; either merging or splintering at it meets its contemporaries. In the past week or so there have been some very interesting reports of studies that all offer new potential insights.