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Topic: Retrograde orbit

Related Topics

Triton (moon)

Kuiper belt

Greek mythology

Rings of Neptune

	Prograde and retrograde motion - Wikipedia, the free encyclopedia
		Retrograde motion is the orbital motion of a body in a direction opposite that which is normal to spatial bodies within a given system.
		However it is possible to observe a body moving west to east, such as an artificial satellite or Space Shuttle that is orbiting eastward (the preferred direction, because the rotation of the Earth assists in acquiring the required orbital speed).
		This is retrogradation, since the planet seems to be moving in a direction opposite to that which is typical for planets.
	en.wikipedia.org /wiki/Retrograde_orbit (799 words)

	Orbit
		Orbits were first analysed mathematically by Kepler who formulated his results in his laws of planetary motion.
		As an object orbits another object, periapsis is that point at which the orbiting object is closest to the object being orbited; apoapsis is that point at which the orbiting object is farthest from the object being orbited.
		An open orbit has the shape of a hyperbola (or in the limiting case, a parabola); the bodies approach each other for a while, curve around each other around the time of their closest approach, and then separate again forever.
	www.brainyencyclopedia.com /encyclopedia/o/or/orbit.html (2044 words)

	Triton (moon) - Wikipedia, the free encyclopedia
		Triton is unique among all large moons in the solar system for its retrograde orbit around the planet (i.e., it orbits in a direction opposite to the planet's rotation).
		Moons in retrograde orbits cannot form out of the same region of the solar nebula as the planets they orbit, but must be captured from elsewhere; it is thought that Triton may be a captured Kuiper belt object.
		Due to its retrograde motion, the already-close Tritonian orbit is slowly decaying further from tidal interactions and it is predicted that between 1.4 and 3.6 billion years from now, Triton will pass within its Roche limit [6].
	en.wikipedia.org /wiki/Triton_(moon) (861 words)

	Prograde and retrograde motion: Definition and Links by Encyclopedian.com - All about Prograde and retrograde motion (Site not responding. Last check: 2007-10-20)
		The moons Ananke, Carme, Pasiphae and Sinope all orbit Jupiter in a retrograde direction, and are thought to be fragments of a single body that Jupiter captured long ago.
		The moon Phoebe orbits Saturn in a retrograde direction, and is thought to be a captured asteroid.
		The moon Triton orbits Neptune in a retrograde direction, and is thought to be a captured Kuiper belt object.
	www.encyclopedian.com /re/Retrograde-orbit.html (760 words)

	Orbit (Site not responding. Last check: 2007-10-20)
		As an object orbits another object, periapsis is that point at which the orbiting object is closest to the object being orbited; apoapsis is that point at which the orbiting object is farthest from theobject being orbited.
		An open orbit has the shape of a hyperbola (or in the limiting case, a parabola); the bodies approach each other for a while, curve around each otheraround the time of their closest approach, and then separate again forever.
		The orbit of a planet around the Sun is an ellipse, with the Sun in one of thefocal points of the ellipse.
	www.therfcc.org /orbit-3594.html (1765 words)

	Orbit Article, Orbit Information (Site not responding. Last check: 2007-10-20)
		Newton showed that a pair of bodies follow orbits of dimensions that are in inverseproportion to their masses about their common center of mass.
		As an object orbits another object, the periapsis is that point at which the orbiting object is closest to the object being orbited and the apoapsis is that point at which the orbiting objectis farthest from the object being orbited.
		In the case of an open orbit,the speed at any position of the orbit is at least the escapevelocity for that position, in the case of a closed orbit, always less.
	www.anoca.org /orbits/object/orbit.html (2031 words)

	ESA - Science - Home - Types of orbit (Site not responding. Last check: 2007-10-20)
		All four classes of orbit are known as ‘conic sections’ because slicing a cylindrical cone in a different way can make each of their shapes.
		A polar orbit is any orbit in which the spacecraft passes over the rotation poles of the planet.
		In a polar orbit, the spacecraft can be made to follow any line of longitude, since these always lead from one pole to the other, and then any line of longitude leads back again on the other side of the Earth.
	www.esa.int /esaSC/SEMU4QS1VED_index_0.html (523 words)

	Basics of Space Flight Section I. The Environment of Space
		The direction a spacecraft or other body travels in orbit can be direct, or prograde, in which the spacecraft moves in the same direction as the planet rotates, or retrograde, going in a direction opposite the planet's rotation.
		It is possible to choose the parameters of a spacecraft's orbit to take advantage of some or all of these gravitational influences to induce precession, which causes a useful motion of the orbital plane.
		A walking orbit whose parameters are chosen such that the orbital plane precesses with nearly the same period as the planet's solar orbit period is called a sun synchronous orbit.
	www2.jpl.nasa.gov /basics/bsf5-1.html (1166 words)

	Retrograde Planets - Bad Astronomy and Universe Today Forum
		Hence, for example, Uranus, whose orbit was initially close to right angles to the final plane of the ecliptic, has a planet spin that was related to that initial orbit in the three dimensional array of matter in the proto Solar System.
		The three dimensional birthplace of the planets meant that a minority of planets had retrograde orbits, and spins associated with that direction, and the action of Sun/Jupiter entrained them to the ecliptic as well, if one studies the gravitational interactions carefully.
		The retrograde spin of Venus is most likely the result of a tidal coupling between the solar torque (which drive Venus towards synchronous rotation) and atmospheric tourque (which drives venus away from synchronous rotation).
	www.bautforum.com /showthread.php?t=3092 (3130 words)

	SPACE.com -- Astronomers Find 11 Tiny Moons around Jupiter
		Their orbits are also "inclined," meaning that they are not in the same plane as Jupiter's equator.
		Retrograde satellites are thought to be space rocks that wandered near Jupiter from elsewhere in the solar system and were captured into orbit.
		Other moons, which orbit in the same direction as the planet spins, are often thought to have formed as a byproduct of planet formation.
	www.space.com /scienceastronomy/solarsystem/jupiter_moons_010109.html (495 words)

	Jupiter's Irregular Satellites
		Because of their orbit characteristics and small size they are believed to be objects captured during the early formation of Jupiter.
		As of 2004, 48 irregular satellites have orbital radii about 300 times the radius of Jupiter (20,000,000 km) and inclinations near 150 to 160 degrees, meaning that they are retrograde or orbit the planet opposite of its rotation.
		The best evidence for capture is that the orbits of some of the irregular moons are actually retrograde (meaning, they orbit the planet in a direction opposite to Jupiter's rotation).
	www.ifa.hawaii.edu /~sheppard/satellites/orbitsall.html (709 words)

	Triton
		retrograde orbits are Jupiter's moons Ananke, Carme, Pasiphae and Sinope and Saturn's Phoebe all of which are less than 1/10 the diameter of Triton.
		Because of its retrograde orbit, tidal interactions between Neptune and Triton remove energy from Triton thus lowering its orbit.
		The unusual nature of Triton's orbit, the similarity of bulk properties between Pluto and Triton, and the highly eccentric, Neptune-crossing nature of Pluto's orbit suggest some historical connection between them.
	www.seds.org /nineplanets/nineplanets/triton.html (729 words)

	Lunar orbit (Henry Spencer)
		This is why the near-equatorial Apollo orbits were retrograde, and why Lunar Prospector's first few lunar orbits didn't (as I recall) involve any interruption of communications.
		To a crude first approximation, an economy trajectory to the Moon is an elliptical orbit with its perigee as low as possible and its apogee at roughly lunar distance.
		It is marginally possible that a carefully-chosen and quite low orbit could exploit lunar mascons to do the same trick, given a complete and detailed understanding of the lunar gravitational field (which we don't have yet), but I wouldn't bet money on it.
	yarchive.net /space/orbits/lunar_orbit.html (1805 words)

	ZetaTalk: Retrograde Orbit
		If the observer is running toward the bird, rocking to the right and left in his running stride, the bobbling of the bird is compounded by the eyes-view of the human runner so that it appears to be jiggling side to side too.
		Astronomers are well aware that the apparent retrograde motion of the outer planets is in fact due to the more rapid orbit of the Earth.
		When at a distance, this energy field affects the 12th Planet but slightly, so it reacts as it approaches from its second foci on the near parallel orbit tracks that it travels upon when moving between its two foci by orbiting in the same manner planets close to the Sun do.
	www.zetatalk.com /science/s85.htm (658 words)

	Orbital Mechanics 101
		A satellite spends the first half of its orbit moving from the perigee to the apogee and the other half of its orbit moving from the apogee to the perigee.
		If a retrograde burn is done at the apogee of an ellipse or on a circular orbit, the orbit becomes more eccentric.
		The new orbit that results from an orbital change maneuver must intersect or touch the old orbit at the location in which the maneuver occurred.
	aerospacescholars.jsc.nasa.gov /HAS/cirr/SS/3/2.cfm (2412 words)

	(none)
		That is, one can capture a planetoid from an orbit that is slightly larger or slightly smaller than the orbit of the planet and the encounter can be in a counterclockwise direction (prograde) or in a clockwise direction (retrograde) as viewed from the north pole of the Solar System.
		The time-scale is long, but the trend is for the circular orbit to get smaller and smaller as the prograde spin rate of the planet decreases and the tides (both ocean and rock tides) become higher in amplitude and frequency.
		The main concept here is that, for a resonant condition, the period of the perigean (or apsidal) cycle of the satellite orbit is equal, or nearly equal, to the period of the heliocentric orbit of the perturbing planet.
	www.denison.edu /geology/malcuit/_malcuit.html (3321 words)

	CE260: Retrograde planets and moons
		The only moons that orbit retrograde are small asteroid-sized distant satellites of giant planets such as Jupiter and Saturn, plus Triton (Neptune's large moon) and Charon (Pluto's satellite).
		The small retrograde satellites of Jupiter and Saturn were probably asteroids captured by the giant planets long after formation of the solar system.
		Venus is rotating retrograde but extremely slowly, with its axis almost exactly perpendicular to the plane of its orbit.
	www.talkorigins.org /indexcc/CE/CE260.html (436 words)

	SeeSat-L Mar-00 : Re: Retrograde orbit (was Unidentified subjec (Site not responding. Last check: 2007-10-20)
		The orbit of all satellites is an ellipse with the gravitational center of the earth's mass as one of the foci.
		The difficult part about retrograde orbits is not maintaining orbit once the satellite gets there, but the fact that whereas launching toward the east takes advantage of the earth's rotation, launching toward the west is fighting the rotation and therefore requires the rocket to first overcome the earth's rotation before obtaining orbital velocity.
		Consequently, payloads launched into retrograde orbit are generally lighter in weight.
	www.satellite.eu.org /seesat/Mar-2000/0029.html (244 words)

	Re: Planet X/12th Planet Retrograde Orbit
		August 29, 1995 a nova The diffuse brightness of an exploding star provides a fairly large area of bright points, as the mass of the star spirals outward with fiercely burning portions away from the star center, which is dimming.
		Along the way they have also lined their fraud up with star clusters and when the orbit was in the comet belt, with faint peripheral comets that JPL and NASA spied with their equipment.
		It is not the many star clusters that the Hale-Bopp orbit was aligned with during its twists and turns that broke all the rules of Orbital Elements and have never been explained by JPL.
	www.zetatalk.com /usenet/use00584.htm (1223 words)

	More on Ofeq, and Some Speculation
		Due to the payload penalty that comes with a retrograde orbit, the westward launch constraint is usually seen as a severe handicap for Israel.
		Ofeq-3's orbit is so phased, and it makes a half-dozen or so daylight passes per day over Israel and the surrounding countries.
		The phasing of the orbit has to be different, but with a constellation of three, both Israel and the South Africans would enjoy uninterrupted multiple daytime passes.
	www.globalsecurity.org /space/library/news/1995/at_950415.htm (681 words)

	Physics Help and Math Help - Physics Forums - Sunrise from west
		Retrograde motion is when an object orbits the other direction.
		Apparent retrograde motion occurs for outer planets, Mars Jupiter, Saturn, Uranus, Neptune and Pluto, when the faster moving earth on the "inner track" of its orbit, overtakes and passes them.
		Venus may have toppled or may have been born retrograde or gravity interaction of its atmosphere with the sun may have induced a slow reversal from a slight prograde spinning to the present retrograde spinning.
	www.physicsforums.com /printthread.php?t=26781&pp=40 (2569 words)

	Retrograde Motion
		To account for the observed retrograde motion of the planets, it was necessary to resort to a system of epicycles, whereby the planets moved around small circular paths that in turn moved around larger circular orbits around the Earth.
		The explanation for retrograde motion in this system arises from the fact that the planets further from the sun are moving more slowly in their orbits than those closer to the sun.
		When combined with the refinements of Kepler (elliptical orbits with the sun at one focus, relationships between distance from sun and orbital speed - both within a single orbit and between orbits) this does, in fact, provide the correct explanation for the observed retrograde motion along with precise predictions of the positions of the planets.
	alpha.lasalle.edu /~smithsc/Astronomy/retrograd.html (696 words)

	overview (Site not responding. Last check: 2007-10-20)
		The small moons orbit in the equatorial plane of the planet, all in a prograde direction.
		There are moons orbiting Jupiter in a retrograde direction, but they are all real small, about a million times less massive than Triton, and its not difficult to imagine how they might have interacted with other larger bodies to have their velocities radically altered.
		Another piece of the puzzle is the fact that the outermost moon, Nereid, has an orbital eccentricity e=0.75 (not a very round orbit at all).
	www.gpc.edu /~fbuls/ast101/part4/nepm.htm (504 words)

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