Tidal forceThe tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field. It causes different parts of bodies to be pulled unevenly, so that those bodies are being stretched towards the attraction. Tidal force is the differential effect of gravity across an extended body. Rather than the total gravitational force, it is the spatial variation in that force.
Tidal lockingAt left, tidally locked, the Moon rotates at the same rate it orbits the Earth, keeping the same face toward the planet. At right, not tidally locked, if the Moon did not rotate then the face would change over the course of an orbit. Viewed from north; not to scale.A side view of the Pluto–Charon system.
Orbital eccentricityIn astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic (escape orbit or capture orbit), and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section.
Rotational energyRotational energy or angular kinetic energy is kinetic energy due to the rotation of an object and is part of its total kinetic energy.
Solar SystemThe Solar System is the gravitationally bound system of the Sun and the masses that orbit it, most prominently its eight planets, of which Earth is one. The Solar System is an isolated single-star planetary system (not part of a larger star system) within the Milky Way Galaxy. The system formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, creating the Sun and a protoplanetary disc from which the orbiting bodies assembled.
Tidal circularizationEffect of tidal forces on an orbiting body Tidal circularization or orbital circularization is an effect of the tidal forces between a body in orbit around a central celestial object, whereby the eccentricity of the orbit is reduced over time so that it becomes less and less elliptical. Typical situation Figure 1: Torque applied to orbit caused by tidal bulge and lag angle In Figure 1, consider two stars, denoted Body 1 and Body 2. Initially think of Body 2 as a point mass.
Io (moon)Io () is the innermost and second smallest of the four Galilean moons of Jupiter. Slightly larger than Earth's Moon, Io is the fourth-largest natural satellite in the Solar System, has the highest density and strongest surface gravity of any natural satellite, and the lowest amount of water by atomic ratio of any known astronomical object in the Solar System. With over 400 active volcanoes, Io is the most geologically active object in the Solar System.
ApsisAn apsis (from Ancient Greek (hapsís)'arch, vault' (third declension); pl.apsides ) is one of the two extreme points in the orbit of a planetary body about its primary body, either the farthest point ('apoapsis) or the nearest point (periapsis). The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two apsides. Apsides pertaining to orbits around different bodies have distinct names to differentiate themselves from other apsides.
Tidal accelerationTidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit (satellite moving to a higher orbit, away from the primary body, with a lower orbital speed and hence a longer orbital period), and a corresponding slowdown of the primary's rotation, known as tidal braking. See supersynchronous orbit.
Elliptic orbitIn astrodynamics or celestial mechanics, an elliptical orbit or eccentric orbit is an orbit with an eccentricity (e) of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. Some orbits with high eccentricity are described as "elongated", but that is not an explanatory term. For the simple two-body problem, all orbits are ellipses.Specific orbital energyIn the gravitational two-body problem, the specific orbital energy ε {\displaystyle \varepsilon } (or specific vis-viva energy) of two orbiting bodies is the constant quotient of their mechanical energy (the sum of their mutual potential energy, ε p {\displaystyle \varepsilon _{p}} , and their kinetic energy, ε k {\displaystyle \varepsilon _{k}} ) to their reduced mass.
Semi-major and semi-minor axesIn geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter.*As an Amazon Associate I earn from qualifying purchases.