What is Orbits: Definition and 497 Discussions

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the center of mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.
For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law. However, Albert Einstein's general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.

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  1. Jenab2

    New and Improved: Elliptical Transfer Orbits determination procedure.

    I was "Jenab" who wrote the "Transfer Orbits for Dummies: A Hillbilly Tutorial" that was stickied in this forum. I've written an improved procedure. The main improvements are: 1. A more straightforward calculation of the true anomaly at the non-apsidal endpoint of the intended trajectory...
  2. P

    The Mysterious Plane of Planetary Orbits

    Why do the elliptical orbits of the planets in our solar system rotate on a single plane.
  3. Y

    Q&A on Orbits: Throwing Balls in Space

    I am new to this forum so do not know all the rules of posting. So please don't mind if I have missed something. I have not been doing any physics and stuff for many many years, but have been having lots of curiosity about stuff, so will dare to ask it here. I understand that orbits are due...
  4. B

    What is the equation for helical path length around a torus?

    Does anyone know the equation for the helical path length around a torus? I need an analytical expression, not an approximation. Thanks
  5. T

    Gravitational Force on satellite orbits

    Homework Statement A satellite orbits Earth 4.0 x 10^{7} m away. The force of gravity between the satellite and Earth is 228 N. What is the mass of the satellite? Homework Equations Fg = (Gm1m2)/(r^{2}) The Attempt at a Solution...
  6. H

    Why most of the planetary orbits are ellipitical?

    theoretically by GMm/r^2 = mv^2/r, planets in a particular distance to the star will move in the corresponding velocity in order to maintain a circular orbit... either over speed they will pass by the star, or under speed they will be attracted towards the star in a spiral way So why are...
  7. A

    Satelites & Orbits: Find the Orbital Speed

    Homework Statement A satelite is placed in orbit 6.00x10^5 meters above the surface of Jupiter which has a mass of 1.90x10^27kg and has a radius of 7.14x10^7m. Find the orbital speed of the satelite Homework Equations V=sqroot(GM/r) The Attempt at a Solution First i added the...
  8. N

    Elliptical Orbits Unfortunately.

    Homework Statement A particular comet has an elliptical orbit. When closest to the Sun (perihelion) it is at a distance of 8.823 x 10^10 m and moves with a speed of 54.6 km/s. The greatest distance between this comet and the Sun (aphelion) is 5.902 x 10^12 m. Calculate its speed at...
  9. S

    Why do planets revolve in elliptical orbits?

    we know that planets revolve in elliptical orbits but Why should planets revolve in elliptical orbits?
  10. J

    Circular Orbits: Sources of Error & Relationship between T and L

    Hi i am doing a lab on circular orbits similar to this one: http://www.batesville.k12.in.us/physics/phynet/mechanics/Circular%20Motion/labs/cf_and_speed.htm I was wondering if someone can tell me what the main sources of error are, as well as the most significant source of error. Also, i...
  11. R

    Radius of Orbits: GPS Satellite & Earth

    Homework Statement A GPS satellite is put in a high circular orbit around the earth. The period of revolution is 8 hours. Calculate the radius r of the orbit, compared to the radius R of the earth. Homework Equations Rearth= 6.4 x 10^6 m mearth= 6 x...
  12. N

    Orbits: explicit r(t) and theta(t)

    I am sure this is a stupid question but can someone give me the equations for r(t) and theta(t) for an orbit an inverse square law (treating the central mass as being at rest). The books always seem to only give r(theta) i.e. the shape of the orbit but not the actual time evolution. Is it ever...
  13. B

    Circular Orbits and Motion - Satellites

    Homework Statement A spy satellite is in circular orbit around Earth. It makes one revolution in 6.02 hours. (Radius of the Earth=6.371 times 106 m) (a) How high above Earth's surface is the satellite? (b) What is the satellite's acceleration? Homework Equations v = sqrt(G*M Earth...
  14. V

    Why does planets hav eliptical orbits

    why does planets hav eliptical orbits (pls explain -not mathematically if posssible)
  15. L

    Satellite Orbits: Measuring Ozone in Antarctic Stratosphere

    What type of orbit would be used for a scientific satellite which needs to take regular readings to measure changes in the concentration of ozone gas in the stratosphere over Antarctica?
  16. H

    The Fascinating Truth About the Moon's Monthly Orbit Around the Earth

    I had no idea it took a month for the moon to orbit the earth. I thought it happened daily, and that's what gave us night. How do we get night?
  17. G

    Bohr's Atom Model: Kepler's Law & Elliptical Orbits

    When bohr gave his model of atom kepler's law already existed ... What made him think that the electrons revolve around the neucleus in circular orbits ? The obvious assumption that should have come to his mind looking at the analogy between the gravitational and electrostatic force should have...
  18. C

    General Relativity: Comparing Newtonian and Einstein Circular Orbits

    i am a physics enthusiast studying general relativity on my own with the book: "Exploring Black Holes: Introduction to General Relativity" by Edwin F. Taylor and John Archibald Wheeler. I am having the hardest time with the fourth chapter of the book and especially the 4th question in that...
  19. M

    The Elliptical Orbits of Comets: Exploring Causes and Consequences

    If the planets are forced into circular orbits by inertia and gravity, why are the orbits of comets oval shaped? What keeps them from entering the sun.
  20. J

    Professionally researched relativistic orbits

    If CarlB (or anyone else) wants to compare his recent results to the relativistic orbits used to make predictions for black hole inspirals by the people who work on LIGO, LISA, VIRGO, TAMA, GEO etc., they are readily available on the web at Living Reviews in Relativity...
  21. R

    Orbits of Andromeda and Milky Way Galaxy About Each Other

    The orbits of the Magellanic Clouds about the Milky Way Galaxy have apparently been determined, and the two dwarf irregular galaxies are now about as close as they will get to the MW in their 2.2 billion year orbit. See p. 42 of "Our Growing, Breathing Galaxy" by Wakker and Richter, Scientific...
  22. O

    Effect of Sun movement on Planetary orbits?

    What is the effect (if any) of the sun's movement around the galactic center in relation to planetary orbits?
  23. A

    Angular momentum in eliptical orbits

    OK, I'm sure I must be doing something wrong here, because I've run into a seeming contradiction. Please refer to the image I've attached below: an ellipse with the center and a focus marked. If there is a massive body at point P, then an object can orbit in the ellipse shown. If I know the...
  24. X

    Bohr radius for single electron orbits

    for ions with more than one proton ie. He+, Li2+ and Be3+, doesn't the extra charge factor into the equation? because it seems only the elementary charge is http://en.wikipedia.org/wiki/Bohr_radius" , hence rendering it independent of amount of positive charge present.
  25. B

    Calculating Frictional Energy Transformation in Satellite Reentry

    Can't really figure out where to start. Any help would be appreciated. Homework Statement A 575 kg satellite is in a circular orbit at an altitude of 550 km above the Earth's surface. Because of air friction, the satellite eventually falls to the Earth's surface, where it hits the ground with...
  26. E

    Electron orbits, QM, Exclusion Principle and location

    I remember that electrons exist in the probability cloud that corresponds to the orbital they reside in, and according to the Pauli Exclusion Principle, they can't share spin in the same orbital. According to the Copenhagen interpretation of quantum mechanics, when the wavefunction is collapsed...
  27. D

    Just a little question on orbits.

    Hi all, Why is it that the planets in our solar system seem to orbit relatively in the same plane? ( or is it a misconception ?) Why can't our planets orbit like this : http://www.steve.gb.com/images/science/planetary.png" Thx.
  28. L

    Periodic Orbits: The Role of the Coulomb Potential in Producing Periodic Motion

    Let's consider the motion of a test particle in a central field. Is the Coulomb potential, 1/r, the only one that produces a periodic motion? If no, is there a condition for periodicity to occur? Thanks, Michel
  29. K

    Seemingly Simple - How Many Orbits? (Rotational Kinematics)

    This is the latest question I've been stuck on. The Bohr model of the hydrogen atom pictures the electron as a tiny particle moving in a circular orbit about a stationary proton. In the n=2 orbit, the distance from the proton to the electron is 21.16e-11 m , and the linear speed of the...
  30. N

    Gravitational Interaction Between Two Orbits

    Two small asteroids orbit each other in circular orbits. The distance between the centers of the two asteroids is 35 m. The mass of the larger asteroid is 3 x 10 6 kg and the mass of the smaller asteroid is 1.2 x 10 5 kg. a. )What is the magnitude of the gravitational force of interaction...
  31. CarlB

    Painleve orbits in Cartesian Coordinates

    With the success of my effort to write the orbits of the Schwarzschild metric in "Cartesian" coordinates, (see https://www.physicsforums.com/showthread.php?t=126996 ) it is now time to compute the orbits for Painleve coordinates. When I'm done, I will have an applet that allows the computation...
  32. V

    Only earth orbits in a circular motion?

    I was reading and came across an article which stated that all the planets orbitted the sun elliptically while the Earth was the only planet to orbit the sun in a circular motion... Is this true? Also what technology did we use to figure this out?? Thanks Vtas25
  33. CarlB

    Schwarzschild Orbits in Cartesian coordinates

    My Java applet gravity simulator http://www.gaugegravity.com/testapplet/SweetGravity.html draws beautiful orbits, however the GR simulation is very badly broken as one can tell when comparing it with Newton at long distances. The source code is at...
  34. M

    Calculating Period of Keplerian Orbit on Mystery Planet

    Hi, I have a question on calculating the period of a planet where I know the gravity at the equator and at the pole. Here is the known information for the planet: Planet radius: 6502 km Planet mass: 4.71 \ast 10^{24} kg An explorer, who weighs 191 lbs on earth, stands at the equator of this...
  35. P

    Does gravity explain all orbits in our solar system?

    Is gravity a sufficient force to explain the movement of the Kuiper Belt around the sun?
  36. S

    The Same Plane: Orbits & Galaxies in Our Solar System

    Why is it that for the most part, all orbiting planets in our solar system orbit together on the same 2D plane. The same can be asked for the disk shape of all of the galaxies. (sp everywhere) Thanks, -scott
  37. M

    Proving Pluto's Orbit Inside Neptune's - Maths Investigation

    Hi guys Im currently investigating planetary orbits in maths and one of our problems is to prove that Pluto spends a good deal of its time inside the orbit of Neptune. If anyone could help that would be great. Thanks Kyle
  38. M

    Proving the Orbits and Partitions Problem in Group Permutations

    Problem: "Let G be a group of permutations of a set S. Prove that the orbits of the members of S constitute a partition of S." I'm a little hazy on how to start this proof. I started by writing down the definition of the Orbit of any element in S. I'm guessing, so correct me if I'm...
  39. C

    The cycle of life? Fractal orbits and spin.

    Greetings, A thought occurs about a (possibly) fundamental pattern in nature. Why are there several scales of magnitude in which a smaller body spins, while orbitting a larger body? Examples. 1) A galaxy like the Milky Way has an orbital momentum around the core of its Local Cluster...
  40. B

    Traveling Electrons: Time to Jump Orbits?

    How many time take to the electron to "Travel" from a lower orbit to a higher one? does it take the same time to travel to the next energy lever or to jump 3 or 4 when hitted by a more energetic photon?? Or it only takes a Planck time since it was hit by the photon?
  41. F

    Orbits and gravitacional field

    Hello, considering a Planet 1 and a Planet 2, where 1 is extremely heavier than 2 and 2 is going in Planet 1's orbit. Two questions 1) howto get the expression v = - G m2 m1 / r 2) if we consider the energy < 0, we can get to an expression as v < sqrt (2GM2 / r) howto get Vx and Vy...
  42. S

    How do Orbits behave as orbital velocities become significantly relatavistic

    I am reasonably familiar with conventional elliptical orbits under gravity but how do they change as orbital velocities get very fast and start approaching the speed of light? let us initially neglect any energy losses due to gravitational radiation. I have been searching the web for some time...
  43. S

    Orbits & Effective Potential: E vs. r Graph Analysis

    attached is the effective potential plotted on E vs r graph. Discuss the nature of the orbits are the various values for r also V_{eff} (r) = - \frac{\alpha}{r} - br^2 - \frac{L^2}{2mr^2} where b << alpha L is the angular momentum and is not zero for R > R5 the orbit is a hyperbola...
  44. V

    Planetary Orbits Around Black Holes

    i know that if a star having planets dies, and becomes a black hole the planets continue to revolve around the black hole. how is it possible when the black hole sucks everything??:confused:
  45. B

    What role do orbits play in Earth's climate change?

    There is a warming cooling pulse in Earth’s life exemplified by tracks left from ancient glaciers to deserts once flush with flora and fauna. When did all this occur and why? Here’s what I think: Moon orbits Earth, Earth orbits Sun, Sun orbits Milky Way, Milky Way orbits ? Each event takes...
  46. S

    Is the Sun Actually Orbiting the Earth?

    Now, the conventional way of viewing the solar system is that all the planets orbit the sun, but since you can declare anything at rest in space, can't you just as easily say that the sun is orbiting the earth, since it will appear that way if you hold the Earth at rest?
  47. P

    How Do You Calculate Total Energy in an Elliptic Orbit?

    How does one derive the total energy in an elliptic orbit: E= - \frac{GMm}{2a} where a is the semi-major axis? I did manage to get the result for the special case of circular orbit, as v = \sqrt{\frac{GM}{R}} But the problem is that I can't figure out a way to express v in an elliptic...
  48. E

    F=mv^2/r and Geosynchronouse orbits

    F=mv^2/r and Geosynchronouse orbits? Help Guys! I’m having a mental block in understanding why geostationary satellites stay in the same place and don’t change orbits or simply fall out of the sky. I may be using inaccurate information so please vet any and all suppositions I make here...
  49. tony873004

    Halo and Lissajous Orbits: Powered or Natural?

    Is a Halo Orbit, such as the one employed by the SOHO spacecraft , a powered orbit (requires corrective burns)?. L1 is unstable, but everything I Google about Halo Orbits seem to suggest that the spacecraft happily orbits the L1 point in a Halo Orbit without corrective burns. Does it do...
  50. P

    Confused on Orbits: Ellipses vs Circles

    As someone who only studied first year physics and maths and have taken no interest in it since than I was rather surprised to wake up one morning and realize along with 99.5% of the population that I really had no idea how the planets orbits worked beyond the vague word ellipse which I didn't...
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