Kell - lent
- Kellner eyepiece
- Kelvin
- Kelvin Helmholtz contraction
- Kelvin timescale
- Keplerian orbits
- Kerr black hole
- kinematic parallax
- kinematics
- kinetic energy
- Kirkwood gaps
- knot
- Kramers opacity
- Kreutz sungrazers
- Kruskal diagram
- L magnitude
- Lagrangian points
- Lambda Eridani stars
- large Magellanic cloud
- large scale structure
- laser ranging
- lasers
- late type dwarf stars
- late type galaxies
- late type giant stars
- late type stars
- late type subdwarf stars
- late type supergiant stars
- late type variable stars
- latitude
- latitude determination
- latitude variation
- LB variable stars
- LC variable stars
- lemaitre universe
- lens antennas
- lens design
- lenses
