Earth, Sun, and Moon Capitalization
Earth, Sun, and Moon are astronomical names, but editorial capitalization can still depend on context and house style. NASA’s Earth Observer explicitly capitalizes all three. Chicago’s reviewed guidance treats the decision more contextually, so the safest editing rule is to follow the governing style consistently rather than turning one publication’s preference into universal grammar.
Capitalize Earth, Sun, and Moon when the governing style treats them as specific astronomical names. Do not assume one universal editorial rule: NASA’s Earth Observer capitalizes all three, while other style systems may allow context-sensitive lowercase treatment.
Key details
Important caveats
Context Boundary
Do not claim that lowercase forms are always wrong or that uppercase forms are always mandatory in every kind of prose. Scientific organizations, publishers, and general style systems can make different editorial choices.
Further guidance
Decision Path
First identify the governing style. If it explicitly treats Earth, Sun, and Moon as proper astronomical names, follow that capitalization consistently. If the style permits context-sensitive treatment, apply its rule rather than importing NASA’s house style automatically.
Nasa House Style
The Earth Observer style guide states that NASA capitalizes Earth, Moon, and Sun. That is strong evidence for NASA/EO copy, but it remains a publication-specific rule.
Worked Examples
NASA/EO-style scientific copy: “Earth orbits the Sun, and the Moon orbits Earth.” General editorial copy: check the required style before changing an established lowercase or uppercase treatment.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Style Guidelines for The Earth Observer Newsletter (opens in a new tab)NASA Science / The Earth Observer · NASA Earth Observer house style explicitly capitalizes Earth, Moon, and Sun. This is a publication-specific style choice, not a universal rule.
- Capitalization Q&A — Earth, Sun, Moon (opens in a new tab)The Chicago Manual of Style · Current Chicago guidance permits capitalization when the bodies are treated as specific astronomical names while also allowing lowercase in ordinary prose; consistency and context matter. This confirms the task is style/context dependent.