Light forces are classified in radiation pressure via resonant absorption with incoherent re-emission and gradient forces via coherent scattering. While usually attributed to laser light, gradient forces also appear in spatially inhomogeneous broadband radiation. Surprisingly, the thermal radiation of a hot sphere can create an attractive net force despite the repulsive radiation pressure. Hence the sun is an optical trap for hydrogen. Novel inter-particle forces also appear via collective scattering of broadband light by several particles. Using quantum optics techniques we propose foundational studies of gradient forces on atoms or nano-particles in generic astrophysical scenarios.