Formation of wide binaries by turbulent fragmentation

Understanding the formation of wide-binary systems of very low-mass stars (M <= 0.1 solar masses, M-circle dot) is challenging(1-3). The most obvious route is through widely separated low-mass collapsing fragments produced by turbulent fragmentation of a molecular core(4,5). However, close binaries or multiples from disk fragmentation can also evolve to wide binaries over a few initial crossing times of the stellar cluster through tidal evolution(6). Finding an isolated low-mass wide-binary system in the earliest stage of formation, before tidal evolution could occur, would prove that turbulent fragmentation is a viable mechanism for (very) low-mass wide binaries. Here we report high-resolution ALMA observations of a known wide-separation protostellar binary, showing that each component has a circumstellar disk. The system is too young(7) to have evolved from a close binary, and the disk axes are misaligned, providing strong support for the turbulent fragmentation model. Masses of both stars are derived from the Keplerian rotation of the disks; both are very low-mass stars.