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Loading contentA grounded explanation of any entity — what it is, how it connects to the rest of the graph, and where the knowledge comes from — assembled entirely from the entity's own description, its relations, and its cited sources.
Three laws describing how planets move: orbits are ellipses with the Sun at one focus; a line from the Sun to a planet sweeps out equal areas in equal times; and the square of a planet's orbital period is proportional to the cube of its…
Assembled entirely from the entity's own description, relations, and cited sources — nothing added.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.