Binaries bend planetary disks

Ars Technica : As giant molecular clouds collapse and shrink, they form stars. In the process, the clouds have to shed angular momentum. More often than not, they do so by breaking up to form two stars that orbit their mutual center of mass. And if either of those stars goes on to form a planetary system, the planets’ orbital planes will tend to align with that of the two stars. Rachel Akeson of Caltech and Eric Jensen of Swarthmore College have found that one binary system, HK Tauri, does not fit the alignment paradigm. Both stars in the system have protoplanetary disks. Using the Atacama Large Millimeter/Submillimeter Array to observe the stars in the far-IR, Akeson and Jensen have determined that the two disks are tilted by 60° to 68° with respect to each other. Although their measurement is relative, not absolute, the astronomers can nevertheless conclude that at least one of the protoplanetary disks is misaligned with respect to the binary system’s orbital plane. The discovery suggests that planetary orbits can be modified while the planetary system is forming.