Cosmologies in which dark matter clumps strongly on small scales are unfavorable to terrestrial detectors that are as yet unexposed to the clumps. I show that subhectometer clumps could trigger thermonuclear runaways by scattering on nuclei in white dwarf cores (carbon and oxygen) and neutron star oceans (carbon), setting off type-Ia-like supernovae and x-ray superbursts, respectively. I consider two scenarios: “dark clusters” that are essentially microhalos and “long-range dark nuggets,” essentially macroscopic composites, with long-range Yukawa baryonic interactions that source the energy for igniting explosions. I constrain dark clusters, weighing between the Planck mass and asteroid masses, and long-range dark nuggets over a wider mass range spanning 40 orders of magnitude. These limits greatly complement searches proposed by myself and co-workers [] for scattering interactions of dark clumps in neutron stars, cosmic rays, and prehistoric minerals. Published by the American Physical Society 2024