hydr - infr
- hydrocarbons
- hydrodynamics
- hydrogen burning
- hydrogen deficient stars
- hydrogen lines
- hydrogen spectrum
- hydromagnetic waves
- hydromagnetics
- hydrostatic equilibrium
- hydroxyl radical
- hyperbolic orbits
- hyperfine lines
- hypergalaxies
- hypergiant stars
- hypothetical planets
- HZ Herculis stars
- I magnitude
- ice
- identification
