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Neptune Note 22 So how do you find a new planet? A. You can use a telescope and randomly hope to find one or... B. Observe another planet for an anomaly that suggests something (like an undiscovered planet) might be affecting its orbit. This is what happened with Neptune. In 1845, 2 mathematicians predicted Neptune based on perturbations in Uranus' orbit - Neptune was discovered in 1846 by a German astronomer using the 1845 predicted position - later that year, another astronomer discovered Neptune's largest moon: Triton More on moons: - Neptune has 8 moons, most of which were discovered by Voyager 2 in 1989. They are: Naiad, Thalassa, Depoina, Galatea, Larissa, Proteus, Triton, Nereid (all named for water gods) - Triton is an unusual moon because it exhibits retrograde orbit (which means it orbits _______?) - it's cold (-393°F) & has Nitrogen geysers, volcanically acitve & probably was captured Meanwhile, back to the planet.... * 3 billion miles from sun * Smallest of Jovian planets – diameter = 30,775 miles Still would hold 60 Earths * Orbital period = 165 years (hasn’t even finished a single orbit around sun since it was discovered!) 5 more years! * Rotation Period = 16 hours * Orbit is not a perfect ellipse (because of _____) Storm Systems here? - Yes, just like Jupiter, Neptune has several monster storm systems that have been swirling around for years The top storm is the “Great Dark Spot”, middle one is “Scooter” and the bottom one is “Great Dark Spot 2” (guess they ran out of names) What about rings? - Neptune has 4 faint, thin rings discovered in 1985 from earth and verified in 1989 by Voyager 2 Voyager and rings of Neptune And the last planet on our tour of the solar system.... Pluto! ? Basic Info: * Smallest planet (9th planet, but sometimes 8th) * Orbital period is 249 years and for 20 or those years (last happened 1979 – 1999) it crosses into Neptune's orbit. This won't happen again until Sep. 2226 :( * Discovered in 1930 while looking for something that seemed to affect Neptune’s orbit At times, people debate whether it is a planet, however it does satisfy the criteria to be a planet: A. it orbits sun B. has strong enough gravity to maintain spherical shape C. has a history of atmosphere Does Pluto have any satellites? Yes, it has one (Charon – approximately the same size as Pluto) Charon Pluto Wait a second, I though moons were supposed to be much smaller than their parent planet. This is yet another reason that Pluto gives astronomers problems in classification. Not only are they about they same size but, they have the same rotational period (6.4 days) Although it is common for a satellite to travel in a synchronous orbit with its planet, Pluto is the only planet to rotate synchronously with the orbit of its satellite. So they always show the same side to each other. Comparison of sizes between Pluto, Charon and the USA