Massive stars, supernovae, and kilonovae are among the most luminous radiation sources in the universe. Observations usually show near-to mid-infrared (NIR-MIR, λ ∼ 1 − 5 µm) emission excess from H II regions around young massive star clusters (YMSCs). Early phase observations in optical to NIR wavelengths of type Ia supernovae also reveal unusual properties of dust extinction and dust polarization. The popular explanation for such NIR-MIR excess and unusual dust properties is the predominance of small grains (size a 0.05 µm) relative to large grains (a 0.1 µm) in the local environment of these strong radiation sources.The question of why small grains are predominant in these environments remains a mystery. Here we report a new mechanism of dust destruction based on centrifugal stress within extremely fast-rotating grains spun-up by radiative torques, which we term the RAdiative Torque Disruption (RATD) mechanism. We find that RATD can disrupt large grains located 1 arXiv:1810.05557v2 [astro-ph.GA] 7 May 2019 within a distance of ∼ 1 pc from a massive star of luminosity L ∼ 10 4 L or a supernova. This effect increases the abundance of small grains relative to large grains and successfully reproduces the observed NIR-MIR excess and anomalous dust extinction/polarization. We apply the RATD mechanism for kilonovae and find that dust within ∼ 0.1 pc would be dominated by small grains. Small grains produced by RATD can also explain the steep far-UV rise in extinction curves toward starburst and high redshift galaxies, and the decrease of the escape fraction of Lyα photons from H II regions surrounding YMSCs.

Dust polarization induced by aligned grains is widely used to study magnetic fields in various astrophysical environments. However, the question of to what optical depth grain alignment still exists in a dense molecular cloud (MC) is unclear. In this paper, we derive analytical formulae for the minimum size of aligned grains (a align) and rotational disruption (a disr) by RAdiative Torques (RATs) as a function of the local physical parameters within MCs. We first find the analytical approximations for the radiation strength and mean wavelength of the attenuated radiation field in a dense MC with and without embedded stars, and then derive analytical formulae for a align and a disr as functions of the visual extinction A V and gas density. We find that, within a starless core of density , grains of size can be aligned at A V  ∼ 5 by RATs, whereas micron-sized grains can still be aligned at . The increase in a align with A V can explain the presence of polarization holes observed toward starless cores. For MCs with an embedded protostar, the efficiency of both alignment and rotational disruption increases toward the protostar due to the increasing radiation strength. Such a disruption effect results in the decrease of the polarization degree with A V or emission intensity, reproducing the popular polarization holes observed toward the location of protostars. Finally, we derive the formula for the maximum A V where grain alignment still exists in a starless core, and we discuss its potential for constraining grain growth.