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A classical planet is an astronomical object that is visible to the naked eye and moves across the sky and its backdrop of fixed stars (the common stars which seem still in contrast to the planets). Visible to humans on Earth there are seven classical planets (the seven luminaries). They are from brightest to dimmest: the Sun, the Moon, Venus ...
Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms direct and prograde are equivalent in this context, the former is the ...
Its diameter is eleven times that of Earth, and a tenth that of the Sun. Jupiter orbits the Sun at a distance of 5.20 AU (778.5 Gm), with an orbital period of 11.86 years. It is the third brightest natural object in the Earth's night sky, after the Moon and Venus, and has been observed since prehistoric times.
Planets in the Solar System. According to the IAU definition, there are eight planets in the Solar System, which are (in increasing distance from the Sun): [2] Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses.
The inner Solar System is the region comprising the terrestrial planets and the asteroids. [ 88 ] Composed mainly of silicates and metals, [ 89 ] the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn.
Comparison of the night sky with the night sky of a hypothetical planet within the Milky Way 10 billion years ago, at an age of about 3.6 billion years and 5 billion years before the Sun formed. [254] Globular clusters are among the oldest objects in the Milky Way, which thus set a lower limit on the age of the Milky Way.
The day 's blue sky, clouds and the Moon. The sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space. In the field of astronomy, the sky is also called the celestial sphere.
The moons Io, Ganymede, Europa, and Titan are visible. A great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky. Great conjunctions occur approximately every 20 years when Jupiter "overtakes" Saturn in its orbit.