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Early works incorrectly depicted Neptune as a solid planet, and several stories thus include human expeditions to its surface. [2] The earliest story where Neptune itself directly appears as a setting is the 1929 short story "A Baby on Neptune" by Clare Winger Harris and Miles J. Breuer, where the planet is covered in ice.
The following list includes some of the potentially habitable exoplanets discovered so far. It is mostly based on estimates of habitability by the Habitable Worlds Catalog (HWC), and data from the NASA Exoplanet Archive.
Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.
Most extrasolar planets in fiction are similar to Earth—referred to in the Star Trek franchise as Class M planets—and serve only as settings for the narrative. [1] [2] One reason for this, writes Stephen L. Gillett [Wikidata] in The Greenwood Encyclopedia of Science Fiction and Fantasy, is to enable satire. [3]
The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently human intelligence, required an improbable combination of astrophysical ...
The discovery of exoplanets, beginning in the early 1990s [8] [9] and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among stars in hosting planets and expands the habitability research horizon beyond the Solar System.
The ice giant planets Uranus and Neptune are thought to have a supercritical water ocean beneath their clouds, which accounts for about two-thirds of their total mass, [30] [31] most likely surrounding small rocky cores, although a 2006 study by Wiktorowicz and Ingersall ruled out the possibility of such a water "ocean" existing on Neptune. [32]
Therefore, the first observations of Neptune were only possible after the invention of the telescope. There is evidence that Neptune was seen and recorded by Galileo Galilei in 1613, Jérôme Lalande in 1795, and John Herschel in 1830, but none are known to have recognized it as a planet at the time. [ 6 ]