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On the other side of Uranus's orbit, the orientation of the poles towards the Sun is reversed. Each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness. [74] Near the time of the equinoxes, the Sun faces the equator of Uranus, giving a period of day–night cycles similar to those seen on most of the other planets.
The moons of the trans-Neptunian objects (other than Charon) have not been included, because they appear to follow the normal situation for TNOs rather than the moons of Saturn and Uranus, and become solid at a larger size (900–1000 km diameter, rather than 400 km as for the moons of Saturn and Uranus).
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
It may also refer to the time it takes a satellite orbiting a planet or moon to complete one orbit. For celestial objects in general, the orbital period is determined by a 360° revolution of one body around its primary, e.g. Earth around the Sun. Periods in astronomy are expressed in units of time, usually hours, days, or years.
Neither the linear speed nor the angular speed of the planet in the orbit is constant, but the area speed (closely linked historically with the concept of angular momentum) is constant. The eccentricity of the orbit of the Earth makes the time from the March equinox to the September equinox , around 186 days, unequal to the time from the ...
the eccentricity of the Earth's orbit around the Sun, which is about 0.0167. The equation of time vanishes only for a planet with zero axial tilt and zero orbital eccentricity. [5] Two examples of planets with large equations of time are Mars and Uranus.
(Escape speed is √ 2 times orbital speed, ... must arrive at the same point in their respective orbits around the Sun at the same time. ... Uranus: 19.19 11.3 15.7 ...
Meteoroids in a retrograde orbit around the Sun hit the Earth with a faster relative speed than prograde meteoroids and tend to burn up in the atmosphere and are more likely to hit the side of the Earth facing away from the Sun (i.e. at night) whereas the prograde meteoroids have slower closing speeds and more often land as meteorites and tend ...