Solar Nebula Magnetic Fields Recorded in the Semarkona Meteorite
Fig 1: Dusty olivine-bearing chondrules from the Semarkona meteorite. Optical photomicrograph of chondrule DOC4 showing the location of dusty olivine grains. Image taken in reflected light with crossed polarizers. [From: Roger R. Fu, et al., "Solar nebula magnetic fields recorded in the Semarkona meteorite," Science DOI: 10.1126/science.1258022. Reprinted with permission from AAAS.]
Magnetic fields are proposed to have played a critical role in some of the most enigmatic processes of planetary formation by mediating the rapid accretion of disk material onto the central star and the formation of the first solids. However, there have been no experimental constraints on the intensity of these fields. A team of researchers from the US, UK, and Denmark, including Harvard Senior Lecturer on Physics Ronald Walsworth, report in the latest issue of Science that dusty olivine-bearing chondrules from the Semarkona meteorite were magnetized in a nebular field of 54 ± 21 μT. This intensity supports chondrule formation by nebular shocks or planetesimal collisions rather than by electric currents, the x-wind, or other mechanisms near the sun. This implies that background magnetic fields in the terrestrial planet-forming region were likely 5-54 μT, which is sufficient to account for measured rates of mass and angular momentum transport in protoplanetary disks.
See the CfA press release.