lightest: proton (uud) and neutron (udd), the only long-lived ones
hyperons (Λ, Σ, Ξ, Ω): contain strange quarks, decay in ~10⁻¹⁰ s
baryon number +1 (antibaryons −1), never observed to change
far more baryons than antibaryons in the universe, origin still unexplained
neutron stars: held up by neutron degeneracy pressure and the short-range repulsion of the strong interaction, maximum mass ≈ 2.2–2.3 solar masses (Fan et al., 2024)
baryonic matter ≈ 5% of the energy content of the universe (dark matter ≈ 27%, dark energy ≈ 68%)