| Abbreviation | Definition |
|---|---|
| SGC | Southern Galaxy Catalogue |
| SGD | Solar Geophysical Data |
| SGRA | School of Galactic Radio Astronomy |
| SGRB(s) | short gamma ray burst(s) |
| SH | Super Hot |
| SHA | Sidereal Hour Angle |
| SIM | Star in Motion |
| SIMBAD | Set Of Identifications Measurements And Bibliography For Astronomical Data |
| SIP | Space Interested Person |
| SIRA | Solar Imaging Radio Array |
| SIS | SETI (Search for Extra-Terrestial Intelligence) Intercept System |
| SJ | Space Junk |
| SKA | Square Kilometre Array |
| SLOI | Satellite Lake Observatory Initiative |
| SLOWPOKES | Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars |
| SLSNe | superluminous supernova events |
| SLSN-I | hydrogen-poor SLSNe |
| SLSN-II | hydrogen-rich SLSNe |
| SLSN-R | radioactively powered SLSNe |
| SMAS | Southern Maryland Astronomical Society |