Habitable zone
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In astronomy and astrobiology, the habitable zone, also known as the circumstellar habitable zone, or as the Goldilocks zone, is the range of orbits around a star within which a planetary surface coul
Edward Walter Maunder, British astronomer, who introduced the concept of habitable zones
Earth's hydrosphere. Water covers 71% of Earth's surface, with the global ocean accounting for 97.3% of the water distribution on Earth.
Natural shielding against space weather, such as the magnetosphere depicted in this artistic rendition, may be required for planets to sustain surface water for prolonged periods.
The habitable zone of Gliese 581 compared with the Solar System's habitable zone
Ocean world
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An ocean world, ocean planet, water world, or water planet is a type of planet or natural satellite that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, eithe
Earth's surface is dominated by the ocean, which forms 71% of Earth's surface. Thus, Earth can be considered a water world, although not a fully oceanic world.
Diagram of the interior of Enceladus. Ice crust Global ocean Rocky core The southern polar region shows active jets.
A set of exoplanets of varying size containing water, compared with the Earth (artist concept; 17 August 2018)
Atacama Large Millimeter Array image of HL Tauri, a protoplanetary disk