| Abbreviation | Definition |
|---|---|
| HBOP | Hale-Bopp comet |
| HCD | High Consistency Discharge |
| HDF | Hubble Deep Field |
| HEAO | High Energy Astronomy Observatory |
| HEO | Highly Elliptical Orbit |
| HESI | High Energy Solar Imager |
| HETE | High Energy Transient Experiment |
| HETE-2 | high energy transient explorer |
| HFQPO(s) | high-frequency quasi-periodic oscillation(s) |
| HGD | Hot Gas Discharge |
| HKO | Hong Kong Observatory |
| HLO | High Light Output |
| HMS | High Mass Star |
| HMSF | High Mass Star Formation |
| HN | Harvard Nebula |
| HO3 | An asteroid /most stable quasi-satellite of Earth |
| HPI | Happy Planet Index |
| HRD | Hertzsprung-Russell Diagram |
| HRG | Hertling Ring Galaxy |
| HRMS | High Resolution Microwave Survey |