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The long orbital period of Neptune means that the seasons last for forty Earth years. [109] Its sidereal rotation period (day) is roughly 16.11 hours. [12] Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme.
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. [a] Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50 × 10 9 km).
It did not take long before d'Arrest exclaimed: "That star is not on the map!". [28] ... "Neptune's Discovery 150 Years Later". Astronomy. 24 (9): 42 ...
The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.
The Solar System is chaotic over million- and billion-year timescales, [102] with the orbits of the planets open to long-term variations. One notable example of this chaos is the Neptune–Pluto system, which lies in a 3:2 orbital resonance .
This long-exposure photo shows Saturn, Venus, Neptune, Uranus, Jupiter and Mars aligning on the same line over the Ispatan plateau in the Iskenderun district of Hatay, Turkey, on January 25.
Given the different Sun incidence in different positions in the orbit, it is necessary to define a standard point of the orbit of the planet, to define the planet position in the orbit at each moment of the year w.r.t such point; this point is called with several names: vernal equinox, spring equinox, March equinox, all equivalent, and named considering northern hemisphere seasons.