Neptune

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Solar System Exploration: Neptune’s Moons

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

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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)
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More News …

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

  • Neptune is cooler than we thought: Study reveals...
    on April 11, 2022 at 2:13 pm

    New research has revealed how temperatures in Neptune's atmosphere have unexpectedly fluctuated over the past two decades.

  • 'Prenatal' protoplanet upends planet formation...
    on April 4, 2022 at 4:04 pm

    An international research team has discovered a new planet so young that it has yet to emerge from the womb of matter where it is forming. This is the youngest protoplanet discovered to date. It's location and the surrounding patterns of matter suggest that an alternative method of planet formation may be at work. This discovery could help to explain the histories and features of extrasolar planets seen around other stars.

  • Puffy planets lose atmospheres, become...
    on February 3, 2022 at 9:12 pm

    Astronomers have identified two different cases of 'mini-Neptune' planets that are losing their puffy atmospheres and likely transforming into super-Earths.

  • Evidence of superionic ice provides new insights...
    on October 14, 2021 at 5:12 pm

    Not all ice is the same. The solid form of water comes in more than a dozen different - sometimes more, sometimes less crystalline - structures, depending on the conditions of pressure and temperature in the environment. Superionic ice is a special crystalline form, half solid, half liquid - and electrically conductive. Its existence has been predicted on the basis of various models and has already been observed on several occasions under - very extreme - laboratory conditions. New results […]

  • To watch a comet form, a spacecraft could tag...
    on October 13, 2021 at 12:15 pm

    A new article proposes that space probes could hitch a ride with 'centaurs' as they become comets. Along the way, the spacecraft would gather data that would otherwise be impossible to record -- including how comets, Earth-like planets, and even the solar system formed.


Phys.org - latest science and technology news stories Phys.org internet news portal provides the latest news on science including: Physics, Nanotechnology, Life Sciences, Space Science, Earth Science, Environment, Health and Medicine.

  • Webb telescope nearly set to explore the solar...
    on May 20, 2022 at 5:51 am

    As NASA's James Webb Space Telescope moves through the final phases of commissioning its science instruments, we have also begun working on technical operations of the observatory. While the telescope moves through space, it will constantly find distant stars and galaxies and point at them with extreme precision to acquire images and spectra. However, we also plan to observe planets and their satellites, asteroids, and comets in our solar system, which move across the background stars of our […]

  • Ceres probably formed farther out in the solar...
    on May 19, 2022 at 2:55 pm

    When Sicilian astronomer Giuseppe Piazzi spotted Ceres in 1801, he thought it was a planet. Astronomers didn't know about asteroids at that time. Now we know there's an enormous quantity of them, primarily residing in the main asteroid belt between Mars and Jupiter.

  • The instability at the beginning of the solar...
    on April 27, 2022 at 6:50 pm

    Michigan State University's Seth Jacobson and colleagues in China and France have unveiled a new theory that could help solve a galactic mystery of how our solar system evolved. Specifically, how did the gas giants—Jupiter, Saturn, Uranus and Neptune—end up where they are, orbiting the sun like they do?

  • Pluto's orbit is surprisingly unstable
    on April 21, 2022 at 4:54 pm

    In 1930, astronomer Clyde Tombaugh discovered the fabled "Ninth Planet" (or "Planet X") while working at the Lowell Observatory in Flagstaff, Arizona. The existence of this body had been predicted previously based on perturbations in the orbit of Uranus and Neptune. After receiving more than 1,000 suggestions from around the world, and a debate among the Observatory's staff, this newfound object was named Pluto—which was proposed by a young schoolgirl from Oxford (Venetia Burney).

  • Astronomers capture surprising changes in...
    on April 11, 2022 at 9:00 am

    An international team of astronomers have used ground-based telescopes, including the European Southern Observatory's Very Large Telescope (ESO's VLT), to track Neptune's atmospheric temperatures over a 17-year period. They found a surprising drop in Neptune's global temperatures followed by a dramatic warming at its south pole.

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