Orbit Definition and 1000 Threads

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. M

    Exploring Electron Orbit: Understanding the Distance from the Atom's Nucleus

    Why are the electrons so far away from the nucleus of an atom ?
  2. DHF

    Will the Moon Ever Escape Tidal Locking?

    The Moon is close enough to Earth that it is tidally locked, however it is also slowly but steadily moving into a wider orbit around Earth. Will there be a point in tile when the Moon is no longer locked and able to freely rotate and if so how far apart would that need to be? Don
  3. R

    Find eccentricity of orbit after star has lost mass

    Homework Statement Initially, a planet with mass m moves on a circular orbit (r = R) around a star with mass M. Now M is instantaneously decreased to M'. Find the eccentricity e of the elliptical orbit the planet now follows. Homework Equations specific angular momentum l = L/m...
  4. C

    Transforming Fields in Inertial and Rotating Frames

    If I am in orbit around Earth that means that I am in constant free-fall around earth. Is this an inertial reference frame?
  5. S

    Pigs in space and circular orbit

    Homework Statement Two particles pigs of mass ##m## and ##M## undergo uniform circular motion about each other at a separation of ##R## under the influence of an attractive force ##F##. The angular velocity is ##\omega## radians per second. Show that R = \frac{F}{\omega^2}\left( \frac{1}{m} +...
  6. P

    What is the radius of the de broglie circular orbit with n=1?

    What is the radius of the de broglie circular orbit with n=1?
  7. S

    Survivable change to the earth’s orbit

    I would like to know in what ways the earth’s orbit might be modified by the close approach of a massive body from beyond the solar system, such as an orphan earth, Jupiter, super Jupiter planet or brown dwarf. The “variables” of interest being the amount of warning we would receive by virtue...
  8. T

    [Dynamic Systems] Computing the orbit of a number

    Homework Statement Choose an even number in the interval [100,199] and compute its orbit under the proper divisor function. Homework Equations Proper Divisor Function = σ(n) = Sum of all divisors of n, excluding n The Attempt at a Solution I am unsure what it means by "compute the...
  9. R

    Angular Momentum in a Kepler Orbit

    I got myself here a satellite rotating at a large distance around planet X. Distance from center of planet X = 100, mass of the satellite = 1 gram (really small), mass of planet X = 1.0 kg velocity of my satellite 10 m/sec and in this oddball universe the gravitational constant = 10**4...
  10. C

    MHB Solving for Central Force in $r = c\theta^2$ Orbit

    Could someone please explain how I work with $-mf(r)e_r$ in this question. Usually we get given an equation (like the one for f(r)) and have to work out the orbit by getting a differential equation etc. I'm not too sure how to work it this way around. "A particle of mass m moves under the...
  11. M

    What gives the electron the energy to continuosly orbit

    What gives the electron the apparently necessary energy to keep orbiting the nucleus for the vast time periods that this has occurred for? The electron is a moving charge, so is there a potential difference making the current flow? Is this something to do with the field of the proton? I...
  12. E

    Do Electrons Orbit Nuclei at the Same Distance?

    Do electrons all orbit an nucleus at the same distance? I.e is an 's' cloud always the same in every atom or does the chance of finding one closer or further to the nucleus change? What about when the spin opposite electron enters the shell?
  13. Y

    Question Regarding the Orbit of Comets

    Recently, I attended a lecture at my university entitled "The Life and Death of a Star-Grazing Comet" presented by John Raymond, an astrophysicist at Harvard Smithsonian. In this lecture, he talked about Comet Lovejoy and how it allowed us to help study the corona of the sun. As the comet was so...
  14. A

    Moon's Orbit: The Science Behind Its Path

    Does the moon's orbit depends mainly on the gravity of Earth and the distance between it and between earth?
  15. G

    Firing an object into orbit using a moon's gravity

    Let's say I'm on a planet and I have a space "gun" that can launch an object upwards at any speed in any direction. Typically with this, you could not launch an object without any rockets into orbit because the best you could do is make the object loop around the planet to exactly where it...
  16. D

    Parametric Equations of Keplerian Orbit

    Homework Statement The figure illustrates a Keplerian orbit, with Cartesian coordinates (x,y) and plane polar coordinates (r,φ). F = -(G*M*m)/r^2 The parametric equations for the orbit: r(ψ) = a ( 1 − e cos ψ) tan(φ/2) = [(1+e)/(1-e)]^(1/2)* tan(ψ/2) t(ψ) = (T/2π) ( ψ − e sin ψ) where ψ is the...
  17. B

    Using Poincare Bendixson's Theorem to prove a periodic Orbit

    Homework Statement The System is x˙ = 2x -y - x(x^2+y^2) y˙ = 5x - 2y(x^2+y^2) Using a trapping region to show there is a periodic orbit Homework Equations Use Poincare Bendixson's TheroemThe Attempt at a Solution I tried constructing 2 Lyapunov type functions to show that DV/dt>0 and...
  18. D

    How Do You Calculate the Eccentricity of an Elliptical Orbit?

    ##\mu_{sun} = 132712000000## ##\mu_{earth} = 398600## ##\mu_{mars} = 42828## ##R_{earth} = 149.6\times 10^6## ##R_{mars} = 227.9\times 10^6## ##r_{earth} = 6378## ##r_{mars} = 3396## The spacecraft will make 3 rev in 2 Earth years. I found the semi-major axis of the ellipse which is...
  19. L

    Can a Photon Have a Perfectly Smooth Orbit?

    can a photon have a perfectly smooth orbit? say for e.g. you have a photon orbiting a point, if its wavelength were to become twice the diameter of its orbit then would the wave not become a replica of the orbit offset by the amplitude? similarly say the amplitude is the radius of the...
  20. Y

    What is the Speed of Earth on its Orbit During Equinoxes and Solstices?

    While the mean speed of the Earth on its solar orbit is about 30km/sec, what is its approximate speed during the both equinoxes and the both solstices ?
  21. D

    Period of circular orbit with in terms of varying speeds and radius.

    Homework Statement A particle of unknown mass moves in a circular orbit of radius R under the influence of a central force centred at some point inside the orbit. The minimum and maximum speeds of the particle are vmin and vmax respectively. Find the orbital period T in terms of these speeds...
  22. C

    Finding parameters of a hyperbolic orbit

    Homework Statement A particle of mass m is moving in a repulsive inverse square law force ##\mathbf{F}(\mathbf{r}) = (\mu/r^2)\hat{r}##. Given that ##u(\theta) = -\frac{\mu}{mh^2} + A\cos(\theta - \theta_o)##, 1) Determine the paramters of the (far branch of the)hyperbolic orbit...
  23. T

    Time taken for earth to orbit the sun?

    Are we just really lucky that the time it takes for Earth to orbit the sun is 365.25 days? I mean if it was something like 365.71 days, then we couldn't have our simple leap year every four years. We would have to have a 71 leap years every century, or even if we were to simplify it a bit, 7...
  24. K

    Calculating Density of a Planet Based on Close Orbit Satellite Period

    A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is 1.94 hours. What is density of the planet? Assume that the planet has a uniform density. density = kg/m^3 T = 2∏/ω = 2∏r/v GMm/r^2 = (mv^2)/r v^2 = GM/r v = rω So I know I...
  25. N

    Conservation of Energy for satellite in an elliptic orbit

    Homework Statement A satellite is in an elliptic orbit around the Earth. Its speed at pedigree A is 8650 m/s. (a) Use conservation of energy to determine its speed at B. The radius of the Earth is 6380 km. Use conservation of energy to determine the speed at the apogee C. Homework...
  26. C

    Particle in an Orbit: Central Force Motion and Radial Equation

    Homework Statement A particle of mass m moves under the influence of a central force $$\underline{F(r)} = -mk\left[\frac{3}{r^2} - 2\frac{a}{r^3}\right] \hat{r}$$ The particle is projected from point A, at a distance a from the centre of force O, in a direction perpendicular to OA, its...
  27. R

    Standing Waves in Bohr's Circular Orbit: Interference Explained

    If electron waves weren't standing waves in Bohr's circular orbit, why and how would the waves interfere ?
  28. K

    Finding the semi-major axis of a transfer orbit?

    Homework Statement Hi, I have a question on my homework that I'm absolutely stuck at. I'm not sure how to go about this. Can someone help me through the steps to solve it? there are more after this similar to it so learning how to do this one would help me do the other ones by my self. Thanks...
  29. C

    Shuttle moving in a circular orbit

    The space shuttle is moving in a circular orbit with a speed of 7.8km/s and a period of 87min. In order to return Earth, the shuttle fires its retro engines opposite to its direction of motion. The engine provide a deceleration of 6m/s^2 that is constant in magnitude and direction. What is the...
  30. R

    Altitude of Satellite Orbit in 4.4 Hours

    1. At what altitude will a satellite complete a circular orbit of the Earth in 4.4 hours? Homework Equations T^2 = ((4π^2)(r^3))/GM The Attempt at a Solution Used the equation and plugged all the information, and solved, but for a weird reason it comes wrong, maybe I should...
  31. B

    Small oscillations and closed orbit

    Homework Statement I'm studying small oscillations. When can I say that an orbit is closed? The Attempt at a Solution I remember that there is a ratio that must be a rational number but I don't remember other thing... Thank you!
  32. C

    Placing a cargo on a parabolic orbit from europa moon of Jupiter

    Hello, The problem is quite simple.You are an astronautics engineer in an established colony on europa,one of jupiter's moons and your boss asks you what would be the minimum velocity so that a cargo full of wastes or garbage is placed on a parbolic (neglecting the mass of europa versus the...
  33. A

    Spin orbit coupling and hydrogen problem

    I don't know if you are familiar with it, but in pertubationt theory for hydrogen it is handy to look for eigenstates of J = L + S since this commutes with the hamiltonian (L and S are not separately conserved). My book then says that the good quantum numbers are: n,l, j, mj I must admit I'm...
  34. A

    Understanding Spin Orbit Coupling: Deriving the Hamiltonian

    I have a question about how my book derives a formula. It starts with: We have an electron free too move on a cylinder and from the cylinder there is an electric field pointing radially outwards. Now for an electron moving in an electric field it sees local magnetic field given by: B =...
  35. H

    Calculating Period of Rotation for Mars-Bound Weight at 3.8 m/s2

    Homework Statement As a spacecraft of diameter 2.8km approaches Mars, the astronauts want to experience what their Mars-bound weight will be. What should the period of rotation be to simulate an acceleration due to gravity of magnitude 3.8 m/s2 ? Mass of Mars = 6.37*1023 Radius of Mars =...
  36. jaumzaum

    Why the electron orbit is a integer multiple of De Broglie wavelength?

    I cannot understand why the electron orbit should be an integer multiple of De Broglie wavelength. Why should the wave path "fit" the electron orbit for it to be stationary?
  37. M

    Comparing the Frequencies of the Moon and Earth's Revolution: Which is Greater?

    Homework Statement Which is greater, the frequency of the Moon’s revolution about the Earth, or the frequency of Earth’s revolution about the Sun? How much (factor) greater? Homework Equations f=1/p p=period The Attempt at a Solution Earth= 1 Revolution/365 days (1 rev/31536000...
  38. G

    Compute Impact Velocity Vector for Orbital Trajectory

    Let's say a craft is in an orbit at a height h above a planet or moon. A force acts directly against the craft's direction of motion so as the force vector is always parallel to the surface of the central body. So, the craft will slowly decelerate and impact the surface. What would be the best...
  39. B

    Energy Considerations When A Satellite Changes Orbit

    Homework Statement A 1 034-kg satellite orbits the Earth at a constant altitude of 102-km. (a) How much energy must be added to the system to move the satellite into a circular orbit with altitude 191 km? (b) What is the change in the system's kinetic energy? (c) What is the change in...
  40. D

    MHB Calculating Elliptical Orbit Points & Flight Path Angle

    Determine the location of the point(s) on an elliptical orbit at which the speed is equal to the (local) circular orbital speed. Determine the flight path angle at this location. What equation(s) should I be using or thinking about for this?
  41. D

    MHB Finding Orbit Type with Energy Equation

    How does one use the energy equation to determine the type of orbit? $$ E = \frac{v^2}{2} - \frac{\mu}{r} $$ where $\mu = G(m_1+m_2)$ and $$ \mathbf{r} = \begin{pmatrix} -4069.503\\ 2861.786\\ 4483.608 \end{pmatrix}\text{km},\quad \mathbf{v} = \begin{pmatrix} -5.114\\ -5.691\\ -1.000...
  42. V

    Could an ion engine attached to a satellite be used to stabilize orbit?

    Basically, my understanding is that every satellite that is not at a lagrange point will see its orbit eventually decay and it will crash back into the earth. Could an ion engine be set to fire at certain times to offset this? Because the rate of decay is slow, an ion engine might be up for it...
  43. E

    Back and forward orbit [around gravitating objects]

    As I figure [and have consulted with some physicists], there no reason why this would not work: object orbiting a planet in one direction, then, half way trough, hits something that propels it in the other direction [at orbital speed, of course], orbits the planet the other way around and hits...
  44. M

    Decaying Moon's Orbit - Physics Modeling Explained

    Hello, Here's my challenge: I want a physics model for how one would go about in order to decay the moon's orbit. I'm assuming it would involve using the velocity vector of the moon whereby Earth would be a reference system, coupled with the mass, and devise a theoretical way of degenerating...
  45. B

    Plot Orbit using Orbital Elements: 2D Analysis

    Homework Statement I want to Plot a Orbit using only the Orbital Elements. The orbit will be two dimensional, so I think some elements will be discarded. Homework Equations The Attempt at a Solution
  46. V

    Maintaining orbit around the moon

    http://news.discovery.com/space/asteroids-meteors-meteorites/lets-put-an-asteroid-into-lunar-orbit-130111.htm Basically, wouldn't any object that orbited around the moon gradually see its orbit be made more and more eliptical until it crashed into the moon itself? Also, it actually takes...
  47. S

    Does the Milky Way Orbit Anything? Investigating Our Galaxy's Center

    Does the milkyway orbits anything ?? like sun orbiting center black hole of our galaxy Does the milkyway orbits anything ?? like sun orbiting center black hole of our galaxy i have this question bcoz our moon moves towards(orbiting) Earth but can't reach or hit Earth bcoz Earth moves...
  48. V

    Is it possible at all to go faster in an orbit around the earth?

    My understanding is that generally with space flight, when you accelerate in the direction of orbit, you don't go around the Earth any faster but instead ascend to a higher orbital plane, which arguably has a longer period of orbit. Is there any manuver method that let's you move around the...
  49. J

    Creating a Generator in Orbit: Where Am I Going Wrong?

    I had a thought. Without friction, the conductor in between the magnet would spin indefinitely in orbit (free of gravity). Tell me where I am going wrong
  50. E

    A question about geosynchronous orbit

    I a question regarding an object, that is originally in geosynchronous orbit, but then thrusted straight down. Will the object land directly on where it was hovering over while in the geosynchronous orbit? Or will it land off target because, as it falls, it's relative position to the Earth is no...
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