The claim refers to the well-established fact that very low-mass stars, red dwarfs, and brown dwarfs can have radii comparable to or even smaller than Jupiter (around 1 R_J). Because this is a standard, universally accepted astronomical fact grounded in basic stellar physics and everyday observations of stellar radii, it falls under common knowledge. None of the retrieved papers specifically target or single out the exact comparison of stellar diameters to Jupiter as their primary thesis in a way that requires formal citation for verification.