S
- Speed Of Light
- Spin-flip Transition
- Spiral Arm
- Spiral Galaxy
- Spiral Galaxy Formation
- Square Kilometre Array
- Standard Candle
- Standardised Candle Method For SNII
- Star
- Starburst Galaxy
- Stellar Association
- Stellar Black Hole
- Stellar Evolution
- Stellar Halo
- Stellar Jets
- Stellar Luminosity Class
- Stellar Populations Of Globular Clusters
- Stellar Winds
- Steradian
- Sublimation
- Summation
- Summer Solstice
- Sun
- Sun-grazing Comet
- Sunspot Cycle
- Superior Conjunction
- Superior Planet
- Supermassive Black Hole
- Supernova
- Supernova Classification
- Supernova Remnant
- Supernova Remnant Type
- Supernova Search
- Supernova Type Ib
- Supernova-Gamma Ray Burst Connection
- Surface Brightness Profiles
- Synchrotron Emission