Neptune

eighth and farthest observed planet in the Solar System

Neptune is the eighth and last planet from the Sun in the Solar System.[12] It is an ice giant.[12] It is the fourth largest planet and third heaviest.[12] Neptune has five rings which are hard to see from the Earth.[12] It is seventeen times heavier than Earth and is a little bit heavier than Uranus.[12] It was named after the Roman God of the Sea.[13][14]

Neptune Neptune symbol.svg
Neptune - Voyager 2 (29347980845) flatten crop.jpg
Photograph taken by NASA's Voyager 2 in 1989
Discovery[1]
Discovered by
Discovery date23 September 1846
Designations
Pronunciation/ˈnɛptjn/ (About this soundlisten)[2]
Named after
Latin Neptunus, via French Neptune
AdjectivesNeptunian (/nɛpˈtjniən/),[3] Poseidean[4]
Orbital characteristics[9][a]
Epoch J2000
Aphelion30.33 AU (4.54 billion km)
Perihelion29.81 AU (4.46 billion km)
30.07 AU (4.50 billion km)
Eccentricity0.008678
367.49 days[6]
5.43 km/s[6]
256.228°
Inclination1.767975° to ecliptic
6.43° to Sun's equator
0.74° to invariable plane[7]
131.784°
2042-Sep-04[8]
276.336°
Known satellites14
Physical characteristics
Mean radius
24,622±19 km
Equatorial radius
24,764±15 km
3.883 Earths
Polar radius
24,341±30 km
3.829 Earths
Flattening0.0171±0.0013
7.6183×109 km2
14.98 Earths
Volume6.254×1013 km3[6]
57.74 Earths
Mass1.02413×1026 kg[6]
17.147 Earths
5.15×105 Suns
Mean density
1.638 g/cm3[6]Based on the volume within the level of 1 bar atmospheric pressure</ref>
11.15 m/s2[6]
1.14 g
0.23[10] (estimate)
23.5 km/s[6]
0.67125 d
16 h 6 m 36 s
(synodic; solar day)[5]
0.6713 day[6]
16 h 6 min 36 s
Equatorial rotation velocity
2.68 km/s (9,650 km/h)
28.32° (to orbit)[6]
North pole right ascension
 19h 57m 20s
299.3°
North pole declination
42.950°
Albedo0.290 (bond)
0.442 (geom.)
Surface temp. min mean max
1 bar level 72 K (−201 °C)[6]
0.1 bar (10 kPa) 55 K (−218 °C)[6]
7.67 to 8.00
2.2–2.4″[6][11]
Atmosphere[6]
19.7±0.6 km
Composition by volume

Neptune's atmosphere is mostly made up of hydrogen and helium. It also contains small amounts of methane which makes the planet appear blue. Neptune's blue color is much darker compared to the color of Uranus.[15] This planet also has the strongest winds of any planet in the Solar System, measured as high as 2,100 km/h or 1,300 mph.[16]

Neptune was discovered by the astronomers Urbain Le Verrier and John Couch Adams.[17][18] They were both honored for the discovery.[19] The planet was the first to be discovered by mathematical calculations instead of using a telescope.[18] In 1821, it was found that Uranus' orbit had some differences from its expected orbit. So astronomers searched for another new planet.[20]

The planet was visited by only one spacecraft, Voyager 2 on 25 August 1989.[21][22] Neptune once had a huge storm known as the "Great Dark Spot" which was discovered in 1989 by Voyager 2. [23][24] However, the dark spot was not seen in 1994, and new spots were found since then. It is not known why the dark spot disappeared.[25] Visits by more space probes have been proposed.[26][27]

HistoryEdit

DiscoveryEdit

The first possible sighting of Neptune is thought to be by Galileo as his drawings showed Neptune near Jupiter.[28] But Galileo was not credited for the discovery since he thought Neptune was a "fixed star" instead of a planet. Because of Neptune's slow movement across the sky, Galileo's small telescope was not strong enough to detect Neptune as a planet.[29]

In 1821, Alexis Bouvard published the astronomical tables of the orbit of Uranus.[30] Later observations showed that Uranus was moving in an irregular way in its orbit.[20] Therefore some astronomers thought of another large body.[20] In 1843, John Couch Adams calculated the orbit of an eighth planet that would possibly be influencing the orbit of Uranus. He sent his calculations to Sir George Airy, the Astronomer Royal, who asked Adams for an explanation. [31]

 
Urbain Le Verrier, the co-discoverer of Neptune.

In 1846, Urbain Le Verrier, who was not working with Adams, made his own calculations but also failed to get much attention from French astronomers.[32] However, in the same year, John Herschel began to support the mathematical method and encouraged James Challis to search for the planet. After much delay, Challis began his unwilling search in July 1846. Meanwhile, Le Verrier had convinced Johann Gottfried Galle to search for the planet.[32]

Heinrich d'Arrest, a student at the Berlin Observatory, suggested the following. A newly drawn map of the sky in the region of Le Verrier's predicted area could be compared with the current sky.[32] It was needed to look for the change of position of a planet, compared to a fixed star. Neptune was then discovered that very night on 23 September 1846, within 1° (one degree (angle)) of where Le Verrier had predicted it to be, and about 10° from Adams' prediction. Challis later found out that he had seen the planet twice in August, failing to recognize it due to his careless work approach.[32]

Crediting and namingEdit

When Neptune was discovered, there was also a lot of arguing between the French and the British. It was about who was to deserve credit for the discovery. Later, an international agreement decided that both Le Verrier and Adams together deserved credit. However, historians reviewed the topic after the rediscovery in 1998 of the "Neptune papers" (historical documents from the Royal Greenwich Observatory). It had seemingly been stolen and kept by astronomer Olin Eggen for nearly three decades and was only rediscovered (in his ownership) shortly after his death.[33] After reviewing the documents, some historians now think that Adams does not deserve equal credit with Le Verrier.[34]

Shortly after its discovery, Neptune was temporarily called "the planet exterior to Uranus" or "Le Verrier's planet". The first suggestion for a name came from Galle. He proposed the name Janus. In England, Challis suggested the name Oceanus.[35] In France, Arago suggested that the new planet be called Leverrier, a suggestion which was met with a lot of opposition outside France. French almanacs quickly reintroduced the name Herschel for Uranus and Leverrier for the new planet.[31]

Meanwhile, Adams suggested changing the name Georgian to Uranus, while Leverrier (through the Board of Longitude) suggested Neptune for the new planet. Struve gave support of that name on 29 December 1846, to the Saint Petersburg Academy of Sciences.[36] Soon Neptune was internationally agreed among many people and was then the official name for the new planet. In Roman mythology, Neptune was the god of the sea, identified with the Greek god, Poseidon.[37]

StructureEdit

Mass and compositionEdit

At 102.413×1024kg[38], Neptune's mass puts the planet between Earth and the largest gas giants. Neptune has seventeen Earth masses but just 1/18th the mass of Jupiter.[39] Neptune and Uranus are often considered to be part of a sub-class of a gas giant known as "ice giants."[40] It is given their smaller size and big differences in composition compared to Jupiter and Saturn. In the search for extrasolar planets, Neptune has been used as a reference to determine the size and structure of the discovered planet. Some discovered planets that have similar masses like Neptune are often called "Neptunes." [41]

The atmosphere of Neptune is made up mostly of hydrogen, with a smaller amount of helium. A tiny amount of methane was also detected in the atmosphere. The methane gives Neptune its blue color.[42]

Because of Neptune's far distance from the Sun, it gets very little heat. The average temperature on Neptune is about -201°C (−331 °F; 72 K).[43] Therefore, Neptune is the coldest planet in the Solar System. But in the depths of planet the temperature rises slowly. The source of this heating is unknown.[44] Neptune is the farthest planet from the Sun, yet its internal energy is strong enough to create the fastest winds seen in the Solar System.[45] Several possible explanations have been suggested. Firstly, radiogenic heating from the planet's core. Among the explanations is the continued radiation into space of leftover heat made by infalling matter during the planet's birth. The last explanation is gravity waves breaking above the tropopause.[46][47]

The structure of the inside of Neptune is thought to be very similar to the structure of the inside of Uranus. [48] There is likely to be a core, thought to be about 15 Earth masses.[1] It is made up of molten rock and metal surrounded by rock, water, ammonia, and methane.[1] This mixture is referred to as icy. It is called a water-ammonia ocean. [49] More mixtures of methane, ammonia, and water are found in the lower areas of the atmosphere. [48]

At a depth of 7, 000 km of Neptune, the conditions may be such that methane decomposes into the diamond crystals. These diamond crystals resemble hailstones.[50][51]

The pressure at the center of Neptune is millions of times more than that on the surface of Earth.[52]

Neptune
Comparison of the size of Neptune and Earth
Internal structure of Neptune
The Great Dark Spot, as seen from Voyager 2

Weather and magnetic fieldEdit

One difference between Neptune and Uranus is the level of meteorological activity that has been observed.[53] When the Voyager spacecraft flew by Uranus in 1986, the winds on that planet were observed to be mild.[53] When Voyager flew by Neptune in 1989, powerful weather events were observed.[53] The weather of Neptune has extremely active storm systems. [45] It's atmosphere has the highest wind speeds in the Solar System, thought to be powered by internal heat flow. Regular winds in the equatorial region have speeds of around 1,200 km/h (750 mph). Winds in storm systems can reach up to 2,100 km/h, near-supersonic speeds.[54]

In 1989, the Great Dark Spot, an anticyclonic storm system, was discovered by NASA's Voyager 2 spacecraft.[23][24] The storm resembled the Great Red Spot of Jupiter. [23] However, on 2 November 1994, the Hubble Space Telescope did not see the Great Dark Spot on the planet. Instead, a new storm similar to the Great Dark Spot was found in the planet's northern hemisphere. [55] The reason why the Great Dark Spot has disappeared is unknown.[25] The Scooter is another storm, a white cloud group farther south than the Great Dark Spot.[56] Its nickname was given when first noticed in the months leading up to the Voyager encounter in 1989.[56] It moved faster than the Great Dark Spot.[57] Later images showed clouds that moved even faster than Scooter. The Wizard's Eye/Dark Spot 2 is another southern cyclonic storm, the second strongest storm seen during the 1989 encounter. It originally was completely dark, but as Voyager came closer to the planet, a bright core developed.[58]

Neptune also has similarities with Uranus in its magnetosphere.[59][60] The magnetic field strongly tilted comparative to its rotational axis at 47° and offset at least 0.55 radii (about 13,500 kilometres) from the planet's physical center. The scientists think the extreme course may be characteristic of flows in the interior of the planet.[59]

Neptune's RingsEdit

 
Neptune's Rings

Tiny blue-colored rings have been discovered around the blue planet. They are not as well known as the rings of Saturn. When these rings were discovered by a team led by Edward Guinan, originally, they thought that the rings might not be complete. However, this was proven wrong by Voyager 2. Neptune's planetary rings have a weird "clumpy" arrangement. The scientists think that it may be because of the gravitational contact with small moons that orbit near them.[61]

Proof that the rings are incomplete first began in the mid-1980s, when stellar occultation were found to rarely show an extra "blink" just before or after the planet occulted the star. Pictures from Voyager 2 in 1989 solved the problem when the ring system was found to have several faint rings. The farthest ring, Adams, has three famous arcs now named Liberté, Egalité, and Fraternité (Liberty, Equality, and Fraternity).[62]

The existence of arcs is tough to understand because the laws of motion would predict that arcs spread out into a single ring in a very short time. The gravitational effects of Galatea, a moon just inward from the ring, are now thought to have created the arcs.[63]

New Earth-based observations published in 2005 appeared to show that Neptune's rings are a lot more unstable than thought before. To be exact, it looks like that the Liberté ring might disappear maybe quickly in less than 100 years. The new observations seem to puzzle our understanding of Neptune's rings into a lot of confusion.[64]

Neptune's moonsEdit

Neptune has a total of 14 known moons.[65] As Neptune was the Roman god of the sea, the planet's moons were named after lesser sea gods or goddesses.[66]

The largest moon, and the only one big enough to have the shape of a sphere is Triton. Triton was discovered on October 10, 1846 by British astronomer William Lassell.[67] Unlike all other large planetary moons, Triton moves in the other direction than the other moons.[68] This shows the moon was probably captured and maybe was once a Kuiper belt object.[68] It is close enough to Neptune to be locked into a synchronous orbit. It is also slowly moving into Neptune and will one day be torn apart when it passes the Roche limit.[69] Triton is the coldest object that has been measured in the Solar System, with temperatures of −235°C (38 K, −392 °F).[70]

Neptune's second known moon (by order of distance), the odd moon Nereid, has one of the most unusual orbits of any satellite in the Solar System.[71]

From July to September 1989, Voyager 2 discovered six new moons of Neptune.[72] Of these, Proteus is the second most massive Neptunian moon.[73] It has only one quarter of 1% of the mass of Triton.[73] Neptune's closest four moons, Naiad, Thalassa, Despina, and Galatea, orbit close enough to be inside Neptune's rings. The next farthest out, Larissa was originally discovered in 1981 when it had occulted a star. [74]The moon was credited for causing Neptune's ring arcs when Voyager 2 observed Neptune in 1989. Five new unusual moons discovered between 2002 and 2003 were announced in 2004.[75][76] The latest moon, Hippocamp, was discovered from examining Hubble Telescope images on 16 July 2013.[77][78]

Moons
Neptune (top) and Triton (bottom)
Triton
Proteus

ObservationEdit

Neptune cannot be seen with naked eye alone, since Neptune's normal brightness are between magnitudes +7.7 and +8.0.[79] It can be out-shined by Jupiter's Galilean moons, the dwarf planet Ceres, and the asteroids 4 Vesta, 2 Pallas, 7 Iris, 3 Juno and 6 Hebe.[80] A telescope or strong binoculars will show Neptune as a small blue dot, similar in appearance to Uranus. The blue color comes from the methane in its atmosphere.[81] Its small obvious size has made it difficult to study visually. Most telescopic data was quite limited until the arrival of the Hubble Space Telescope and large ground-based telescopes with adaptive optics.[82]

With an orbital period (sidereal period) of 164.88 Julian years, Neptune was returning to the same place in the sky where it was discovered in 1846. In August 2011, it completed its first full orbit of the Sun. [83] It happened three different times, also with a fourth in which it came very close to being at that position. [84] This is explained by the idea of retrogradation.[84]

ExplorationEdit

Currently, only one spacecraft has visited Neptune. NASA's Voyager 2 probe made a quick flyby of the planet with its closest encounter on 25 August 1989. It was the last planet to have been visited by a spacecraft.[21]

One of Voyager 2's important discoveries was its very close fly-by of Triton where took pictures of several parts of the moon.[85] The probe also discovered the Great Dark Spot. However, it had now disappeared after the Hubble Space Telescope took pictures of Neptune in 1994. Originally thought to be a large cloud or cyclonic storm system.[86] It was later guessed to be a hole in the visible cloud deck.[87]

The pictures sent back to Earth from Voyager 2 in 1989 became the basis of a PBS all-night program called Neptune All Night.[88]

After the Voyager 2 flyby mission comes Flagship orbital mission.[26] This hypothetical mission is not possible until the late 2020s or early 2030s. [26]

Neptune Odyssey is the current mission concept for a Neptune orbiter. NASA's possible large strategic science mission would launch in 2033 and arrive at Neptune in 2049.[27]

ReferencesEdit

  1. 1.0 1.1 1.2 Hamilton, Calvin J. (4 August 2001). "Neptune". Views of the Solar System. Retrieved 13 August 2007.
  2. Walter, Elizabeth (21 April 2003). Cambridge Advanced Learner's Dictionary (2nd ed.). Cambridge University Press. ISBN 978-0-521-53106-1.
  3. "Neptunian". Oxford English Dictionary. Oxford University Press. 2nd ed. 1989.
  4. "Enabling Exploration with Small Radioisotope Power Systems" (PDF). NASA. September 2004. Archived from the original (PDF) on 22 December 2016. Retrieved 26 January 2016.
  5. 5.0 5.1 Seligman, Courtney. "Rotation Period and Day Length". Archived from the original on 11 August 2011. Retrieved 13 August 2009.
  6. 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 Williams, David R. (1 September 2004). "Neptune Fact Sheet". NASA. Archived from the original on 1 July 2010. Retrieved 14 August 2007.
  7. Souami, D.; Souchay, J. (July 2012). "The solar system's invariable plane". Astronomy & Astrophysics. 543: 11. Bibcode:2012A&A...543A.133S. doi:10.1051/0004-6361/201219011. A133.
  8. "HORIZONS Web-Interface". ssd.jpl.nasa.gov.
  9. Yeomans, Donald K. "HORIZONS Web-Interface for Neptune Barycenter (Major Body=8)". JPL Horizons On-Line Ephemeris System. Archived from the original on 20 August 2014. Retrieved 18 July 2014.—Select "Ephemeris Type: Orbital Elements", "Time Span: 2000-01-01 12:00 to 2000-01-02". ("Target Body: Neptune Barycenter" and "Center: Solar System Barycenter (@0)".)
  10. de Pater, Imke; Lissauer, Jack J. (2015). Planetary Sciences (2nd updated ed.). New York: Cambridge University Press. p. 250. ISBN 978-0-521-85371-2. Archived from the original on 26 November 2016. Retrieved 17 August 2016.
  11. Espenak, Fred (20 July 2005). "Twelve Year Planetary Ephemeris: 1995–2006". NASA. Archived from the original on 5 December 2012. Retrieved 1 March 2008.
  12. 12.0 12.1 12.2 12.3 12.4 "In Depth | Neptune". NASA Solar System Exploration. Retrieved 14 June 2021.
  13. "Neptune". nineplanets.org. Retrieved 5 November 2010.
  14. "StarChild Question of the Month for August 2002". NASA. August 2002. Retrieved 5 November 2010.
  15. "Neptune". NASA. Retrieved 11 November 2010.
  16. Suomi, V. E.; Limaye, S. S.; Johnson, D. R. (1991). "High winds of Neptune - A possible mechanism". Science. 251: 929–932.
  17. "Neptune: The First Planet Discovered by Mathematical Rather than Observational Means: Discovered Simultaneously by Le Verrier and Adams : History of Information". Jeremy Norman's History of Information. Retrieved 14 June 2021.
  18. 18.0 18.1 "In Depth | Neptune". NASA Solar System Exploration. Retrieved 14 June 2021.
  19. "Urbain Le Verrier". StarChild. Retrieved 14 June 2021.
  20. 20.0 20.1 20.2 [Anon.] (2001) "Bouvard, Alexis", Encyclopædia Britannica, Deluxe CDROM edition
  21. 21.0 21.1 Chang, Kenneth (18 August 2014). "Dark Spots in Our Knowledge of Neptune". The New York Times. ISSN 0362-4331. Retrieved 15 May 2021.
  22. "Exploration | Neptune". NASA Solar System Exploration. Retrieved 15 May 2021.
  23. 23.0 23.1 23.2 "Hubble captures birth of giant storm on Neptune". ScienceDaily. Retrieved 12 June 2021.
  24. 24.0 24.1 "What is the Great Dark Spot?". Cool Cosmos. Retrieved 12 June 2021.
  25. 25.0 25.1 Sromovsky, L. A.; Fry, P. M.; Dowling, T. E.; Baines, K. H. (2000). "The unusual dynamics of new dark spots on Neptune". Bulletin of the American Astronomical Society. 32: 1005
  26. 26.0 26.1 26.2 Clark, Stephen. "Uranus, Neptune in NASA's sights for new robotic mission – Spaceflight Now". Retrieved 10 May 2021.
  27. 27.0 27.1 Abigail Rymer; Brenda Clyde; Kirby Runyon (August 2020). "Neptune Odyssey: Mission to the Neptune-Triton System"(PDF). Retrieved 10 May 2021.
  28. Hirschfeld, Alan (2001). Parallax:The Race to Measure the Cosmos. New York, New York: Henry Holt. ISBN 0-8050-7133-4.
  29. Littmann, Mark; Standish, E.M. (2004). Planets Beyond: Discovering the Outer Solar System. Courier Dover Publications. ISBN 978-0-486-43602-9.
  30. A. Bouvard (1821), Tables astronomiques publiées par le Bureau des Longitudes de France,kikin, FR: Bachelier
  31. 31.0 31.1 "John Couch Adams' account of the discovery of Neptune". Maths History. Retrieved 10 May 2021.
  32. 32.0 32.1 32.2 32.3 Airy, G. B. (1 January 1970). "Account of some circumstances historically connected with the discovery of the Planet exterior to Uranus". Astronomische Nachrichten No. 585. doi:10.1002/asna.18470251002.
  33. Kollerstrom, Nick (2001). "Neptune's Discovery. The British Case for Co-Prediction". University College London.
  34. William Sheehan, Nicholas Kollerstrom, Craig B. Waff (December 2004). The Case of the Pilfered Planet - Did the British steal Neptune? Scientific American.
  35. Moore, Patrick (2000). The Data Book of Astronomy. pp. 206.
  36. Hind, J. R. (1847). "Second report of proceedings in the Cambridge Observatory relating to the new Planet (Neptune)". Astronomische Nachrichten. 25: 309. Smithsonian/NASA Astrophysics Data System (ADS).
  37. "Enabling Exploration with Small Radioisotope Power Systems" (PDF). web.archive.org. 22 December 2016. Retrieved 10 May 2021.
  38. "Neptune Fact Sheet". nssdc.gsfc.nasa.gov. Retrieved 14 June 2021.
  39. Bradford A. Smith, «Neptune », World Book Online Reference Center,‎ 2004, p. 5
  40. Helled, Ravit; Nettelmann, Nadine; Guillot, Tristan (25 March 2020). "Uranus and Neptune: Origin, Evolution and Internal Structure". Space Science Reviews. 216 (3): 38. doi:10.1007/s11214-020-00660-3. ISSN 1572-9672.
  41. "Trio of Neptunes". Astrobiology Magazine. 21 May 2006. Retrieved 9 June 2021.
  42. "All About Neptune | NASA Space Place – NASA Science for Kids". spaceplace.nasa.gov. Retrieved 12 June 2021.
  43. "Solar System Temperatures". NASA Solar System Exploration. Retrieved 12 June 2021.
  44. Elkins-Tanton, Linda T. (2006). Uranus, Neptune, Pluto, and the Outer Solar System. Infobase Publishing. p. 75. ISBN 978-1-4381-0729-5.
  45. 45.0 45.1 Cain, Fraser (9 December 2008). "What is the Weather Like on Neptune?". Universe Today. Retrieved 12 June 2021.
  46. McHugh, J. P., Computation of Gravity Waves near the Tropopause Archived 27 October 2007 at the Wayback Machine, AAS/Division for Planetary Sciences Meeting Abstracts, p. 53.07, September 1999
  47. McHugh, J. P., and Friedson, A. J., Neptune's Energy Crisis: Gravity Wave Heating of the Stratosphere of Neptune, Bulletin of the American Astronomical Society, p.1078, September 1996
  48. 48.0 48.1 Hubbard, W.B. (1997). "Neptune's Deep Chemistry". Science. 275 (5304): 1279–80.
  49. Atreya, S.; Egeler, P.; Baines, K. (2006). "Water-ammonia ionic ocean on Uranus and Neptune?" (PDF). Geophysical Research Abstracts. 8. 05179.
  50. Kerr, Richard A. (October 1999). "Neptune May Crush Methane Into Diamonds". Science. 286 (5437): 25a–25.
  51. Kaplan, Sarah (25 August 2017). "It rains solid diamonds on Uranus and Neptune". The Washington Post. ISSN 0190-8286. Retrieved 12 June 2021.
  52. "Interior Models of Jupiter, Saturn and Neptune" (PDF). GSI Helmholtz Center. 18 July 2011. Retrieved 10 May 2021.
  53. 53.0 53.1 53.2 The Sun, Planets, and Dwarf Planets. PediaPress.
  54. Hammel, H.B.; et al. (1989). "Neptune's wind speeds obtained by tracking clouds in Voyager images". Science. 245: 1367–1369.
  55. Hammel, H. B.; Lockwood, G. W.; Mills, J. R.; Barnet, C. D. (23 June 1995). "Hubble Space Telescope Imaging of Neptune's Cloud Structure in 1994". Science. 268 (5218): 1740–1742. doi:10.1126/science.268.5218.1740. ISSN 0036-8075.
  56. 56.0 56.1 "Neptune Scooter". The Planetary Society. Retrieved 15 June 2021.
  57. "Planet Neptune | Introduction to Astronomy". courses.lumenlearning.com. Retrieved 15 June 2021.
  58. "Catalog Page for PIA00064". Jet Propulsion Laboratory California Institute of Technology. Retrieved 10 May 2021.
  59. 59.0 59.1 Stanley, Sabine; Bloxham, Jeremy (11 March 2004). "Convective-region geometry as the cause of Uranus' and Neptune's unusual magnetic fields". Nature. 428 (6979): 151–153. doi:10.1038/nature02376.
  60. Helled, Ravit; Nettelmann, Nadine; Guillot, Tristan (25 March 2020). "Uranus and Neptune: Origin, Evolution and Internal Structure". Space Science Reviews. 216 (3): 38. doi:10.1007/s11214-020-00660-3. ISSN 1572-9672.
  61. Schörghofer, Norbert; Hsieh, Henry H. (2018). "Ice Loss From the Interior of Small Airless Bodies According to an Idealized Model". Journal of Geophysical Research: Planets. 123 (9): 2322–2335. doi:10.1029/2018je005568. ISSN 2169-9097.
  62. Cox, Arthur N. (2001). Allen's Astrophysical Quantities. Springer. ISBN 978-0-387-98746-0.
  63. "In Depth | Neptune". NASA Solar System Exploration. Retrieved 10 May 2021.
  64. "Neptune's rings are fading away". New Scientist. 26 March 2005. Retrieved 9 June 2021.
  65. "Nasa's Hubble telescope discovers new Neptune moon". BBC. 15 July 2013. Retrieved 16 July 2013.
  66. "Planet and Satellite Names and Discoverers". Gazetteer of Planetary Nomenclature. U.S. Geological Survey.
  67. "In Depth | Triton". NASA Solar System Exploration. Retrieved 13 June 2021.
  68. 68.0 68.1 Agnor, Craig B.; Hamilton, Douglas P. (2006). "Neptune's capture of its moon Triton in a binary–planet gravitational encounter." Nature. 441 (7090): 192–94.
  69. Jankowski, David G.; Chyba, Christopher F.; Nicholson, Philip D. (1989). "Tidal evolution in the Neptune-Triton system". Astronomy and Astrophysics. 219 (1–2): L23–L26.
  70. Nelson, R.M.; Smythe, W.D.; Wallis, B.D.; Horn, L.J.; et al. (1990). "Temperature and Thermal Emissivity of the Surface of Neptune's Satellite Triton." Science. 250 (4979): 429–31.
  71. "In Depth | Nereid". NASA Solar System Exploration. Retrieved 11 June 2021.
  72. Stone, E.C.; Miner, E.D. (1989). "The Voyager 2 Encounter with the Neptunian System". Science. 246 (4936): 1417–21.
  73. 73.0 73.1 "Planet Neptune's moons". The New Times | Rwanda. 29 May 2010. Retrieved 15 June 2021.
  74. "In Depth | Larissa". NASA Solar System Exploration. Retrieved 15 June 2021.
  75. Holman, Matthew J. (19 August 2004). "Discovery of five irregular moons of Neptune". Nature. 430: 865–867.
  76. "Five new moons for planet Neptune". BBC News. 18 August 2004. Retrieved 6 August 2007.
  77. "Nasa's Hubble telescope discovers new Neptune moon". BBC News. 15 July 2013. Retrieved 13 June 2021.
  78. Grush, Loren (20 February 2019). "Neptune's newly discovered moon may be the survivor of an ancient collision". The Verge. Retrieved 10 May 2021.
  79. Mallama, A.; Hilton, J.L. (2018). "Computing Apparent Planetary Magnitudes for The Astronomical Almanac". Astronomy and Computing. 25: 10–24.
  80. See the respective articles for magnitude data.
  81. Moore, Patrick (2000). The Data Book of Astronomy. pp. 207.
  82. "APOD: 2000 February 18 - Neptune through Adaptive Optics". apod.nasa.gov. Retrieved 10 May 2021.
  83. Gaherty, Geoff (12 July 2011). "Neptune Completes First Orbit Since Its Discovery in 1846". Space.com. Retrieved 10 May 2021.
  84. 84.0 84.1 Anonymous (2 May 2013). "Horizons Output for Neptune 2010–2011". Retrieved 11 May 2021.
  85. Greicius, Tony (17 February 2015). "Voyager Map Details Neptune's Strange Moon Triton". NASA. Retrieved 11 June 2021.
  86. Steigerwald, Bill (14 March 2019). "Hubble Tracks the Lifecycle of Giant Storms on Neptune". NASA. Retrieved 11 June 2021.
  87. "Neptune's Great Dark Spot of 1989" Windows to the Universe
  88. Phillips, Cynthia (3 November 2007). "Fascination with Distant Worlds". Retrieved 10 May 2021.
Notes
  1. Orbital elements refer to the Neptune barycentre and Solar System barycentre. These are the instantaneous osculating values at the precise J2000 epoch. Barycentre quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis from the motion of the moons.

Other websitesEdit