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Giant planets


Orbiting the Sun at a mean distance of 30 AU, with a revolution period of almost 165 years, Neptune is the outmost of the giant planets, and also the smallest. Its diameter is 49,530 km, i.e., 3.9 times the terrestrial value. Still, its mass (17 terrestrial masses) is slightly greater than Uranus’ and its density (1.64 g/cm3) is thus also larger. Both Uranus and Neptune are called “icy giants” because most of their mass is contained in the icy core from which they accreted. As all other giant planets, Neptune is surrounded by a system of rings and satellites.


History of Observations

Neptune was first identified in 1846 by Johannes Galle, who followed the prediction of Urbain Le Verrier, based on celestial mechanics calculations. The quest for Neptune had started after the discovery of Uranus in 1781, as it was realized that Uranus’ orbit was perturbed by another more distant heavy body. John Couch Adam from Cambridge University and Urbain Le...

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  • DOI: 10.1007/978-3-642-11274-4_1047
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Neptune. Figure 1

References and Further Reading

  • Cruikshank DP (1995) Neptune and Triton. University of Arizona Press, Tucson, Arizona

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  • Gibbard SG et al (2003) The altitude of Neptune's cloud features from high-spatial resolution near-infrared spectra. Icarus 166:359–374

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  • Hammel HH et al (1989) Neptune's wind speed obtained by tracking clouds in Voyager images. Science 245:1367–1369

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  • Lunine JI (1993) The atmospheres of Uranus and Neptune. Annu Rev Astron Astrophys 31:217–263

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  • Orton GS et al (2007) Evidence for methane escape and strong seasonal and meridional perturbations of Neptune's atmospheric temperatures. Astron Astrophys 473:L5–L8

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  • Pearl JC, Conrath BJ (1991) The albedo, effective temperature, and energy balance of Neptune, as determined from Voyager data. J Geophys Res Supp 96:18921–18930

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  • Smith BA et al (1989) Voyager 2 at Neptune: imaging science results. Science 246:1422–1449

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Correspondence to Therese Encrenaz .

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© 2011 Springer-Verlag Berlin Heidelberg

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Encrenaz, T. (2011). Neptune. In: , et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg.

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