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Mercury attains an inferior conjunction (nearest approach to Earth) every 116 Earth days on average, [4] but this interval can range from 105 days to 129 days due to the planet's eccentric orbit. Mercury can come as near as 82,200,000 km (0.549 astronomical units; 51.1 million miles) to Earth, and that is slowly declining: The next approach to ...
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 ...
Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or nutation of an object's rotational axis. Prograde or direct motion is more normal motion in the same ...
In 20 cases, Mercury goes into a dangerous orbit and often ends up colliding with Venus or plunging into the Sun. Moving in such a warped orbit, Mercury's gravity is more likely to shake other planets out of their settled paths: In one simulated case, Mercury's perturbations sent Mars heading toward Earth. [12]
In astronomy, the rotation period or spin period[1] of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space).
Kepler's laws of planetary motion. Illustration of Kepler's laws with two planetary orbits. The orbits are ellipses, with foci F1 and F2 for Planet 1, and F1 and F3 for Planet 2. The Sun is at F1. The shaded areas A1 and A2 are equal, and are swept out in equal times by Planet 1's orbit. The ratio of Planet 1's orbit time to Planet 2's is.
Compared to many extrasolar systems, the Solar System stands out in lacking planets interior to the orbit of Mercury. [ 70 ] [ 71 ] The known Solar System lacks super-Earths , planets between one and ten times as massive as the Earth, [ 70 ] although the hypothetical Planet Nine , if it does exist, could be a super-Earth orbiting in the edge of ...
Orbits. The inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the orbital plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator.