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Netuno é o oitavo planeta a partir do sol. Ele é um gigante gasoso.
Neptune is the eighth planet from the sun. It is a gas giant.
After the discovery of Uranus, it was noted that the orbits of Uranus, Saturn, and Jupiter were apparently being perturbed by an additional unknown mass in the outer solar system. John Couch Adams and Urbain Jean Joseph Le Verrier used calculations to predict the region of the sky where the mysterious additional planet was likely to be located, and it was subsequently independantly discovered by the German astronomer Johann Gottfried Galle of Berlin Observatory on September 23 1846. Later it was found that Galileo had much earlier observed Neptune. Evidence of the fact was found in his notes, but he had thought it was a star. Had he observed Neptune only a matter of days earlier, its orbital motion would have been far more obvious. With an orbital period of 165 years, Neptune will first return to the point in its orbit where Galle discovered it in 2011. Due to Pluto's eccentric orbit, Neptune is sometimes the farthest known planet from the Sun.
Neptune is never visible with the naked eye. With the use of a telescope it appears as a blue-green disk, similar in appearance to Uranus; the blue-green colour comes from the methane in its atmosphere. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25 1989.
Orbiting so far from the sun Neptune receives very little heat. Its 'surface' temperature is -218 degrees Celsius (below zero). However, the planet seems to have an internal source of heat. It is thought that this may be leftover heat generated by infalling matter during the planet's birth, now slowly radiating away into space. Neptune's atmosphere has the highest wind speeds in the solar system, up to 2000 km/h, thought to be powered by this flow of internal heat.
Neptune's atmosphere contains :
Neptune has a faint planetary ring system of unknown compostion. The rings have a peculiar "clumpy" structure, the cause of which is not currently known but which may involve gravitational interaction with small moons in orbit near them. Evidence that the rings are incomplete first arose in the mid-1980s, when stellar occultation experiments were found to occasionally show an extra "blink" just before or after the planet occulted the star. Images by Voyager 2 in 1989 settled the issue, when the ring system was found to contain several faint rings, the outermost of which, Adams, contains three prominent arcs now named Liberty, Equality and Fraternity. The existence of arcs is very difficult to understand because the laws of motion would predict that arcs spread out into a uniform ring over very short timescales. The gravitational effects of Galatea, a moon just inward from the ring, are now believed to confine the arcs. Several other rings were detected by the Voyager cameras. In addition to the narrow Adams Ring 63,000 km from the center of Neptune, the Leverrier Ring is at 53,000 km and the broader, fainter Galle Ring is at 42,000 km. A faint outward extension to the Leverrier Ring has been named Lassell; it is bounded at its outer edge by the Arago Ring at 57,000 km.
Data for Neptune:
| Name | Orbital radius (km) | Diameter (km) | Mass (kg) |
|---|---|---|---|
| Naiad | 48,200 | 58 | Unknown |
| Thalassa | 50,000 | 80 | Unknown |
| Despina | 52,600 | 148 | Unknown |
| Galatea | 62,000 | 158 | Unknown |
| Larissa | 73,600 | 193 (208 x 178) | Unknown |
| Proteus | 117,600 | 418 (436 x 416 x 402) | Unknown |
| Triton | 354,760 | 2700 | 2.14×1022 |
| Nereid | 5,513,400 | 340 | Unknown |
Solar system:
Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets
