? Aurigae is a bright, eclipsing binary star system but the cause of each 18-month-long eclipse has been unknown for nearly 190 years, because the companion was, until recently, undetectable. The preferred explanation has been a tilted disk of opaque material and here the authors report interferometric images that do indeed show an opaque disk of very low mass, tilted as expected, crossing the disk of the F star

The strength of conventional metals is determined by the interaction of dislocations with obstacles such as grain boundaries. Molecular dynamics simulations reveal that the strength of ultrafine-grained copper containing twin boundaries can be controlled by a dislocation nucleation mechanism activated below a critical twin thickness. Below this thickness the material becomes softer. The smaller the grains, the smaller the critical twin boundary spacing, and the higher the metal's maximum strength

Here a method of seismic wave imaging known as 'ambient noise' tomography is used to generate high-resolution images of seismic wave speeds in the crust and uppermost mantle. The observations reveal strong and uniform anisotropy — where waves travel through rock at different speeds depending on direction — in the deep crust in areas of the western United States that have undergone significant extension during the past 65 million years