January 2021
Vol 7, Issue 1

About The Cover

Cover image expansion

ONLINE COVER Theorists have proposed for decades that protoplanetary disks—rotating accumulations of dense gas and dust that surround newly formed stars—contain substantial magnetic fields that contribute to the formation of planets. However, until recently, scientists have lacked evidence for the existence of these key magnetic fields. This began to change in 2014, when studies of ancient traces of magnetism in meteorites, induced at the time of their formation, detected evidence for a nebular field in our own system. These findings hold important implications for understanding the lifetime of the gas and dust cloud and the formation of the Sun, giant planets, and mineral grains in stony meteorites. In a review of these groundbreaking paleomagnetic data, Weiss et al. describe how the findings support the proposal that magnetism was central to mass and angular momentum transport in the protoplanetary disk and chronicle how these insights relate to the fields of paleomagnetism, meteoritics, astronomy, and magnetohydrodynamics. [CREDIT: BENJAMIN WEISS]