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Solar System Exploration: Neptune’s Moon Triton (NASA)
Solar System Exploration: Neptune’s Moons



Physical Realm
Universe Astronomical Instrument
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid


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Solar System Exploration: Neptune (NASA)
Neptune Portal (Wikipedia)
Neptune Category (Wikipedia)


Neptune : the planet eighth in order from the sun — Webster

Oxford, OneLook, Free Dictionary, Wiktionary, Urban Dictionary


Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×109 km). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune’s trident.

Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet’s remaining known 14 moons were located telescopically until the 20th century. The planet’s distance from Earth gives it a very small apparent size, making it challenging to study with Earth-based telescopes. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989. The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar.

Neptune’s composition can be compared and contrasted with the Solar System’s other giant planets. Like Jupiter and Saturn, Neptune’s atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but it contains a higher proportion of “ices” such as water, ammonia, and methane. However, its interior, like that of Uranus, is primarily composed of ices and rock, which is why Uranus and Neptune are normally considered “ice giants” to emphasise this distinction. Traces of methane in the outermost regions in part account for the planet’s blue appearance.

In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune’s atmosphere has active and visible weather patterns. For example, at the time of the Voyager 2 flyby in 1989, the planet’s southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 kilometres per hour (580 m/s; 1,300 mph). Because of its great distance from the Sun, Neptune’s outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K (−218 °C). Temperatures at the planet’s center are approximately 5,400 K (5,100 °C). Neptune has a faint and fragmented ring system (labelled “arcs”), which was first detected during the 1960s and confirmed by Voyager 2. — Wikipedia

Neptune (Eric Weisstein’s World of Astronomy, Wolfram Research)
Encyclopædia Britannica







Neptune in Depth (NASA)


WorldCat, Library of Congress, UPenn Online Books, Open Library



All About Neptune (Space Place, NASA)
Neptune (Cosmos4Kids)


Crash Course Astronomy (YouTube)

OER Commons: Open Educational Resources



NASA, Science Daily,




Neptune (NASA)





OEDILF: The Omnificent English Dictionary In Limerick Form



Neptune News -- ScienceDaily Planet Neptune News. Read astronomy articles on Neptune's oddball moon Triton. See images of Neptune and more.

  • TESS discovers three new planets nearby,...
    on July 29, 2019 at 3:13 pm

    NASA's Transiting Exoplanet Survey Satellite, or TESS, has discovered three new worlds that are among the smallest, nearest exoplanets known to date. The planets orbit a star just 73 light years away and include a small, rocky super-Earth and two sub-Neptunes -- planets about half the size of our own icy giant.

  • Atmosphere of midsize planet revealed by Hubble,...
    on July 2, 2019 at 8:46 pm

    Two NASA space telescopes have identified the detailed chemical 'fingerprint' of a planet between the sizes of Earth and Neptune. No planets like this can be found in our own solar system, but they are common around other stars.

  • How icy outer solar system satellites may have...
    on June 25, 2019 at 1:33 pm

    Beyond the orbit of the planet Neptune, there are a multitude of icy and rocky small bodies, smaller than planets but larger than comets. These likely formed at the same time as the Solar System, and understanding their origin could provide important clues as to how the entire Solar System originated. Using sophisticated computer simulations and observations of TNOs, astronomers have shown how these so-called trans-Neptunian Objects (or TNOs) may have formed.

  • Astronomers find 'Forbidden' planet in 'Neptunian...
    on May 28, 2019 at 11:30 pm

    An exoplanet smaller than Neptune with its own atmosphere has been discovered in a region close to its star where no Neptune-sized planets would normally be found.

  • Neptune's moon Triton fosters rare icy union
    on May 22, 2019 at 6:17 pm

    Astronomers using the Gemini Observatory explore Neptune's largest moon Triton and observe, for the first time beyond the lab, an extraordinary union between carbon monoxide and nitrogen ices. The discovery offers insights into how this volatile mixture can transport material across the moon's surface via geysers, trigger seasonal atmospheric changes, and provide a context for conditions on other distant, icy worlds. - latest science and technology news stories internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

  • Rocky, Earth-sized exoplanet is missing an...
    on August 20, 2019 at 11:00 am

    Astronomers at MIT, Harvard University, and elsewhere have searched a rocky, Earth-sized exoplanet for signs of an atmosphere—and found none.

  • How astronomers chase new worlds in TESS data
    on August 15, 2019 at 3:00 pm

    As pink liquid oozed around her shoes, astronomer Johanna Teske started to feel sick. She had been looking for new planets with the Planet Finder Spectrograph, an astronomical instrument resembling an industrial-sized refrigerator mounted to the Magellan II telescope. One night in October 2018, a hose leading to the instrument burst, causing pink coolant to spill onto sensitive parts of the instrument and the surrounding platform. Would Teske's search be ruined?

  • A brief astronomical history of Saturn's amazing...
    on August 15, 2019 at 1:10 pm

    Many dream of what they would do had they a time machine. Some would travel 100 million years back in time, when dinosaurs roamed the Earth. Not many, though, would think of taking a telescope with them, and if, having done so, observe Saturn and its rings.

  • Meteorite strikes made life on Earth possible
    on August 13, 2019 at 11:14 am

    Meteorites from the far reaches of the solar system delivered large amounts of water, carbon and volatile substances to the Earth. Only then could the Earth host life. Dr. María Isabel Varas-Reus, Dr. Stephan König, Aierken Yierpan and Professor Dr. Ronny Schönberg from Tübingen University's Isotope Geochemistry Group, and Dr. Jean-Pierre Lorand from the Université de Nantes, provide evidence for this scenario in a new study. Using a method recently developed at the […]

  • The uncertainty of detecting planets
    on August 2, 2019 at 1:10 pm

    Uncertainty in science is a good thing. Because here's how the scientific model works: you observe a phenomenon, then form a hypothesis about why that phenomenon is taking place, then test the hypothesis, which leads you to develop a new hypothesis, and so on. That process means it can be difficult to ever definitely know something. Instead, scientists work to understand the uncertainty in their measurements, their models, their conclusions.