This article says that a magnetic linkage between spinning stars and the charged particles in the dusty disks that surround them slowed the spin of the stars, but says nothing about its effect on the disk. The law of conservation of angular momentum dictates that the angular momentum lost by the star would be transferred to the charged particles in the disk, presumably raising their orbits around the star. Did the researchers comment on this or the potential effects that it might have on planet formation?

John A. Black Jr.
Tempe, Ariz.

Astronomer Luisa Rebull of the California Institute of Technology in Pasadena says that angular momentum is indeed being transferred from a star to its disk. However, she adds that her team, as a “humble observer,” was concerned only with the effect on the stars. —R. Cowen