* 1989 – Voyager 2 spacecraft makes its closest approach to Neptune, the second to last planet in the Solar System at the time.

* 1612 – Galileo Galilei becomes the first astronomer to observe the planet Neptune, although he mistakenly catalogued it as a fixed star.

The hydrogen and helium in " traditional " gas giants like Jupiter and Saturn constitutes most of the planet, whereas the hydrogen / helium only makes up an outer envelope on Uranus and Neptune which are sometimes called ice giants, as they are mostly composed of water, ammonia, and methane molten ices.

Remotely guided space probes have flown by all of the planets of the Solar System from Mercury to Neptune, with the New Horizons probe currently en route to fly by the dwarf planet Pluto and the Dawn spacecraft en route to the dwarf planet Ceres.

* 1983 – Pioneer 10 becomes the first man-made object to leave the central Solar System when it passes beyond the orbit of Neptune ( the furthest planet from the Sun at the time ).

* 1735 – Mathematical calculations suggest that it is on this day that dwarf planet Pluto moved inside the orbit of Neptune for the last time before 1979.

Neptunium ( named for the planet Neptune, the next planet out from Uranus, after which uranium was named ) was discovered by Edwin McMillan and Philip H. Abelson in 1940 at the Berkeley Radiation Laboratory of the University of California, Berkeley.

The Nereids are the namesake of one of the moons of the planet Neptune.

Depiction of Haumea ( dwarf planet ) | Haumea's presumed 7: 12 resonance with Neptune in a rotating frame, with Neptune ( blue dot at lower right ) held stationary.

The dwarf planet Pluto is following an orbit trapped in a web of resonances with Neptune.

The next largest body in a similar 2: 3 resonance with Neptune, called a plutino, is the candidate dwarf planet Orcus.

Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit.

The search began in the mid-19th century and culminated at the start of the 20th with Percival Lowell's quest for Planet X. Lowell proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the gas giants, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities.

These were taken to indicate the existence of yet another planet orbiting beyond Neptune.

He postulated, based largely on simple subtraction from Le Verrier's calculations, that another planet of roughly 12 Earth masses, which he named " Hyperion ", must exist beyond Neptune.

His hypothetical planet, which he termed " Planet O " ( because it came after " N ", i. e. Neptune ), possessed a mean orbital radius of 51. 9 AU and an orbital period of 373. 5 years.

Lowell's greatest contribution to planetary studies came during the last decade of his life, which he devoted to the search for Planet X, a hypothetical planet beyond Neptune.

( Uranus and Neptune were also Greek and Roman gods, but neither planet was known in Antiquity because of their low brightness.

* Thalassa ( moon ), a moon of the planet Neptune

** 93. neptunium, Np, named after the planet Neptune, as it follows uranium and Neptune follows Uranus in the planetary sequence ( 1940 ).

The radio emission of a planet was first detected in 1955, when Burke and Franklin ( 1955 ) identified the origin of interference-like radio noise on their records at about 15 meters wave length as emission from Jupiter.

She was the sun, he the closest planet orbiting around her, the rest of the world existing and visible yet removed.

Part of the time saved was spent on a preliminary estimate for a long-distance plan to free bound oxygen in the sands of Mars to make the planet more friendly to future human generations.

`` That it had found a planet on which human beings could live and which was already inhabited by sentient beings ''!!

Was B'dikkat a crazy slave to his own duty or was he a man who had hopes of going back to his own planet some day, surrounded by a family of little cow-people resembling himself??

These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System were discovered, their volatile-based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids.

* In the Star Wars prequels, the galactic capital planet Coruscant has buildings many miles tall, and approaches the completely built-over condition of Trantor in Isaac Asimov's classic Foundation trilogy ( Note: due to this, Coruscant was originally to be named Jhantor but was eventually renamed Coruscant ).

Early in the Cenozoic, following the K-Pg event, the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians.

The Blue Planetary was discovered by John Herschel and named for its color's similarity to Uranus, though the nebula is three times larger than the planet.

he added: Closely examined, painstakingly studied, she is easily the most interesting person on the planet, and in several ways as easily the most extraordinary woman that was ever born upon it.

While a young researcher working for the Lowell Observatory in Flagstaff, Arizona, Tombaugh was given the job to perform a systematic search for a trans-Neptunian planet ( also called Planet X ), which had been predicted by Percival Lowell and William Pickering.

This ruled out classification as an asteroid, and they decided this was the ninth planet that Lowell had predicted.

The name " Pluto " was reportedly suggested by Venetia Burney, then an 11-year-old English school girl, who died in April 2009, having lived to see the reclassification of Pluto as a dwarf planet.

It was the first comet observed to be orbiting a planet, and had probably been captured by the planet around 20 – 30 years earlier.

Brian Marsden of the Central Bureau for Astronomical Telegrams noted that the comet lay only about 4 degrees from Jupiter as seen from Earth, and that while this could of course be a line of sight effect, its apparent motion in the sky suggested that it was physically close to the giant planet.

Its orbit around Jupiter was very loosely bound, with a period of about 2 years and an apojove ( the point in the orbit farthest from the planet ) of.

Its orbit around the planet was highly eccentric ( e = 0. 9986 ).

While the impacts took place on the side of Jupiter hidden from Earth, Galileo, then at a distance of 1. 6 AU from the planet, was able to see the impacts as they occurred.

A few minutes after the impact fireball was detected, Galileo measured renewed heating, probably due to ejected material falling back onto the planet.

* Cybergirl Cybergirl is a cyber replicant prototype 6000, a " cyborg " from a distant planet who ran away to explore the beings she was created after, human beings.

* In the Stargate Atlantis fifth season episode " Remnants ", a device is found whose purpose was to seed a planet with silicon-based life.

It is later revealed that Tiberium was introduced to Earth by the Scrin, an extremely advanced race of Tiberium-based aliens bent on mining the planet after the Tiberium deposits have reached maturity.