What is Orbit: Definition and 1000 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.

View More On Wikipedia.org
Recent contents Top users
  1. P

    I How many degrees / radians is one full orbit of the Earth?

    One day consists of slightly more than 360° of rotation (360.9856°) on it's axis (due to Earth's orbit around the Sun). I imagine that one orbit is also either > or < 360° around the sun, relative to the motion of the sun around some object. Is this true, or is the orbit of the Earth...
  2. U

    I Circular orbit + small radial oscillation about circular orbit

    The potential energy of a particle of mass $m$ is $U(r)= k/r + c/3r^3$ where $k<0$ and $c$ is very small. Find the angular velocity $\omega$ in a circular orbit about this orbit and the angular frequency $\omega'$ of small radial oscillation about this circular orbit. Hence show that a nearly...
  3. Y

    Push Mercury out to Venus' orbit?

    So it would be cooler and mine-able? Given unlimited tech and wealth in a fictional setting.
  4. T

    Solution to the Two-Body Problem: Cross-Product and Dot-Product Integration

    Homework Statement Two-body problem given as $$\ddot{\textbf{r}}+\frac{GM}{r^2}\frac{\textbf{r}}{r}=0$$ $$\textbf{h}=\textbf{r}\times\dot{\textbf{r}}$$ where the moment of the momentum vector mh Homework Equations The vector solution to the above equation may be obtained by first taking the...
  5. Bob Jones

    How to get tangential velocity

    I am in the process of making a program that visually shows an elliptical orbit over time. I wish to find the tangential velocity of the satellite in the elliptical orbit based on the variables that I know. Here is what I know: a) The angle relative to the right focus with 0 radians being the...
  6. L

    Maple Computational Hohmann Transfer on MapleSoft

    Hi, I am trying to recreate an Interplanetary Hohmann transfer orbit from Earth to Mars similar to image A below (the red line). However, Earths orbit is not circular, It is more of an elliptical orbit rather than circular. I was able to successfully plot the orbits of both Earth and Mars...
  7. J

    Mechanical energy for planet in elliptical orbit around star

    Homework Statement A planet is in an elliptical orbit around a star. Which of the following best represents the mechanical energy E_planet of just the planet and the mechanical energy Es_tar-planet of the star-planet system as functions of time for one complete orbit? Homework Equations...
  8. T

    B Orbit circularisation/insertion spreadsheet

    I am trying to create a spreadsheet that will calculate: The minimum delta-v required to circularise the orbit of a projectile that has been fired horizontally from the Earths surface at a given velocity. Completely ignoring atmospheric drag. See the attached spreadsheet. The steps are...
  9. Rifat amin

    Can two planets share the same orbit without catastrophic consequences?

    can two planets share the same orbit
  10. CrosisBH

    Why Does My VPython Moon Orbit Simulation Not Maintain a Circular Path?

    Code: https://pastebin.com/5LajNBpj So I was messing with VPython, trying to create an Earth-Moon System. I got the actual gravity to work, and can create some nice ellipical orbits. However I run into trouble trying to make the actual (almost) circular orbit of the moon. I know that the...
  11. D

    Mercury's orbit according to Classical VS Modern Physics

    Hello, I'm a high-school student and I was assigned to do this kind of a paper as a senior (one of the requirements of graduating is a short monograph on a subject of interest.) My topic includes an analysis of Mercury's orbit using Newton and Kepler's equations and comparing the predicted...
  12. Toreno

    Calculating orbits of planets in Solar System

    Hi, I am about to write a simple application, simulating in 3D current location of the planets in Solar system. Honestly, I do not know even how to start. Can you please guide me where could I find some good information on planet orbits, current locations and how to make all of the calculations...
  13. Clara Chung

    Criteria for Determining Satellite's Return from Orbit?

    Homework Statement Homework Equations Conservation of energy/ angular momentum The Attempt at a Solution I used conservation of momentum to do part d. My answer is VB/VA=sinα /X. i don't know how to do part e. What is the criteria to determine whether the satellite will return to the...
  14. J

    Total energy of a body in a circular orbit

    Homework Statement Homework Equations The Attempt at a Solution Is the particle moving under the influence of a single central force ? Since the force always acts towards the center , work done by the force is zero . Energy is conserved . Potential energy at a particular radius can be...
  15. M

    I Clarification of a specific orbit example

    Hello, In my professor's lecture notes she gives this example and I have a couple of questions regarding it:Let M = \mathbb Z/6\mathbb Z and f: M \rightarrow M, x \rightarrow x+1 the cyclical permutation of the elements from M. Then is G := \{id_M, f, f^2,f^3,f^4,f^5\} a subset from S_M...
  16. NatanijelVasic

    I "Unexpected" Symmetry in Elliptical Orbit

    Hello everyone :) Not too long ago, I was thinking about planetary motion around a sun, both with circular orbits and elliptic orbits. However, when thinking a little longer about these two cases in a broader sense, I spotted a big difference which I found quite odd (assume purely classical...
  17. amjad-sh

    The origin of spin orbit coupling

    I have read in the internet that "One naturally derive the dirac equation when starting from the relativistic expression of kinetic energy: ##\mathbf H^2=c^2\mathbf P^2 +m^2c^4## where ##\mathbf P## is the canonical momentum. Inclusion of electric and magnetic potentials ##\phi## and ##A## by...
  18. Jan Berkhout

    Having trouble working out centripetal force?

    Homework Statement The Russian Mir space station had a mass of 130 tonnes and orbited Earth at an altitude of 480km with an orbital speed of 7621.4m/s. The diameter of Earth is 12 760 km. a) What centripetal force was acting on it? b) Find the value of the acceleration due to...
  19. J

    Tension of Rope: Cosmonaut & Spaceship Orbit in Planetary Gravity

    Homework Statement What is the tension of this rope? Cosmonaut m=100kg is outside of spaceship M=5 tons on rope with length 64m. Cosmonaut along with his spaceship moves in orbit at a neglible distance. m=100kg M=5000kg L=64m Planet's mass 6*10^24 Planet's radius 6400km Homework Equations...
  20. Physics345

    Time Dilation & 2 Atomic Clocks (one in orbit)

    Homework Statement Two atomic clocks are synchronized. One is placed on a satellite, which orbits around the Earth at a high speed for a whole year. The other is placed in a lab and remains at rest, with respect to the earth. You may assume that both clocks can measure time accurately to many...
  21. DLeuPel

    I How can General Relativity explain the Moon drifting apart from Earth

    According to various sources, the Moon is separating from Earth 4 cm every year. I’ve searched for the explanation and I’ve found the following: The friction the seas and oceans from the Earth make with it’s soil causes the Earth’s rotation to slow down. This causes the Moon to speed up...
  22. lc99

    Calculating Orbital Speed Using Conservation of Angular Momentum

    Homework Statement The dwarf planet Pluto orbits very ellipticaly... Pluto's nearest (perihelion) and farthest (apihelion) distances from the Sun are 30 AU and 50 AU, respectively. (One AU or Astronomical Unit=the mean distance from the center of the Earth to Astronomical Unit = the mean...
  23. A

    I Changing the ISS's orbital inclination to match the Moon

    What is the practical feasibility of changing the International Space Station's orbital inclination to match the orbit of the Moon? Major future missions beyond the Earth-Moon system (ie: space colonization) will likely require in-orbit assembly of components from multiple launches. And...
  24. Specter

    Finding the radius of the satellite's circular orbit

    Homework Statement My title was supposed to say "Finding the radius of the satellites circular orbit" but I can't seem to edit it. << Mentor Note -- Title fixed for you >> A 500 kg satellite experiences a gravitational force of 3000 N, while moving in a circular orbit around the earth. a)...
  25. M

    I Orbit simulations, tidal forces and planetary oblateness

    How does one correct for tidal forces when (classically) simulating the orbits of solar system bodies?
  26. V

    Use angular momentum to find the velocity (comet orbit)

    Homework Statement A comet orbits the sun. It's position in polar coordinates is given by, $$r(\phi)=\frac{1.8r_0}{1+0.8\cos{\phi}},$$ where ##r_0## is the position at closest approach. Its velocity at this point is given by ##v_0##. Use the concept of angular momentum to find the following...
  27. L

    Doubling speed in circular orbit to attain elliptical orbit

    Homework Statement A satellite is in a circular orbit (radius R) around a planet of mass M. To change the satellite's orbit the engines fire and its speed is suddenly doubled. The engines fire for a very short time. Determine the length of the semi-major axis of the new orbit. Homework...
  28. A

    Satellites and the Earth's Magnetic Field

    So i was just wondering if a satellite's circuitry could be affected by the Earth's own magnetic field inducing a current, if it was moving through it quickly enough (the space station for example), and how it might mess with it? Also considering a satellite is a big hunk of metal, could passing...
  29. quasarLie

    A Black Hole Orbit Inequality: Explained

    Hello, Here's an interesting question inspired by a homework probem (not mine), we know that circular orbit (for scjwarzchild black hole) exist only if L ≥ sqrt3 c Rsch=Lisco . Where does this inequality come from? do you have a lecture which can help me to understand? Thanks
  30. Pushoam

    Frequency of a proton moving in a circular orbit

    Homework Statement Homework EquationsThe Attempt at a Solution [/B]Assuming that the relation ## v = \omega r ## is valid in relativistic calculation. As the speed is greater for higher kinetic energy, ## \omega_2 ## is greater. This is shown by only (d). So, I think (d) should...
  31. Rednecknav

    I Calculating Energy to Remove Space Debris from Earth Orbit

    How much energy needs to be be expended to throw a non operating satellite (or other space trash) out of orbit (L4 or L5) or L2 into deeper space... thus minimizing space debris in Earth orbit. I could only find formulas for getting an object INTO orbit... Background of question: we were...
  32. S

    How to calculate ambient temperature in space or in orbit?

    How would I go about calculating the ambient temperature in low Earth orbit (LEO) at approximately 400 km? What equations should I be referencing to determine the temperature of sun light side and/or eclipse side? Thanks!
  33. S

    Why Is the Calculated Wavelength Incorrect in This Hydrogen Atom Problem?

    Homework Statement Calculate energy of electron in first excited state of hydrogen atom. Homework Equations n=2 when i use E=-13.6 (z/n)^2 and then use E=hc/lamda(wavelength) then wavelength is coming wrong The Attempt at a Solution the correct answer is 6.68 armstrong.
  34. Buzz Bloom

    I Tidal effects on Earth's rotation and moon's orbit

    Issues about two topics were discussed in another thread. https://www.physicsforums.com/threads/do-solar-tides-affect-Earth's-orbit.933073/ The topics are: how do the lunar tides (1) cause the Earth's rotation to slow down, and (2) cause the moon to move away from the Earth. This thread is...
  35. Buzz Bloom

    I Do Solar Tides affect Earth's Orbit?

    Solar tides on the Earth are currently approximately 1/2 as strong as lunar tides. The lunar tides affect the Earths rotation as well as the moon's orbit. Therefore it seems plausible that the solar tides would affect the sun's rotation and the Earth's orbit. Can someone confirm for me that...
  36. PsychonautQQ

    A Why Does the Orbit Space of a Covering Map Not Necessarily Equal the Base Space?

    Suppose ##q: E-->X## is a covering map (not necessarily normal). Let ##E' = E/ Aut_{q}(E)## be the orbit space, and let ##\pi: E-->E'## be the quotient map. Then there is a covering map ##q': E' --->X## such that ##q' * \pi = q## where ##*## is composition of functions. I am confused why ##E'##...
  37. A

    I Enforcing artificial frozen orbit

    Hello, I'm interested in how to formulate a simple constellation in which there are two satellites with identical orbital parameters (eccentricity <0.003, same inclination and aligned arg. Perigee, same RAAN) but which have different altitudes (e.g. Semi major axis) which are around 1000km and...
  38. A

    Finding the speed to orbit Deimos

    Homework Statement They stated in the problem that the radius is 6.3. Why did they multiply it by 10^3 during the calculation? Homework Equations It's in part 1 and 3. The Attempt at a Solution [/B]
  39. A

    Is Angular Momentum Conserved During the Changing of the String Length?

    Homework Statement An object with mass m is attached to a string with initial length R, and moves on a frictionless table in a circular orbit with center C as shown in the figure. The string is also attached to the center, but its length is adjustable during the motion. The object initially...
  40. B

    Does the moon orbit as a classical particle?

    The moon orbits Earth at a radius of 3.84E8 m. To do so as a classical particle, its wavelength should be small. But small relative to what? Being a rough measure of the region where it is confined, the orbit radius is certainly a relevant dimension against which to compare the wavelength...
  41. Peter Coe

    Change in momentum for a satellite in circular orbit

    Homework Statement A satellite is in a circular orbit passing over the North and South geographical poles as it orbits the Earth. It has a mass of 2200kg and its orbit height is 870km above the Earth's surface. What is the change in momentum of the satellite from when it passes over the...
  42. F

    I Can two gravitational waves orbit each other?

    Since gravitational waves have energy, they can curve space all by themselves. I wonder in what conditions, if any, two gravitational waves could orbit each other. Thanks.
  43. Noisy Rhysling

    B We have kittens in orbit around Saturn

    Cosmic Kittens: Saturn Features Get Feline Names By Hanneke Weitering, Space.com Staff Writer | September 25, 2017 07:00am ET I f you know anything about Saturn, you probably know that it's a planet surrounded by rings. But did you know that it's also surrounded by cats? NASA's Cassini...
  44. L

    I Can 2 spheres orbit each other say inside ISS?

    I was thinking about two spheres of lead, 1 Kg and if I remember right would be about 3 cm radius. So inside the ISS in microgravity could the gravitational attraction of the two spheres allow them to orbit one another? I calculated an orbital time, if 2 cm apart of about one hour per orbit...
  45. S

    Additional Velocity Required for a Satellite Already in Orbit to Escape

    Homework Statement A satellite is orbiting the Earth around an orbit of radius R=2.5R0, where R0 is Earth's radius. What additional velocity is needs to be directed along the radius of the orbit so that satellite escapes Earth's gravity? Homework Equations Total Energy= K + U Conservation of...
  46. T

    B Space Stationary Orbit: Possible to Park Ship for 1 Year?

    Is it possible to park a ship say halfway between the Earth and the moon and stay there for about a year and watch the Earth and moon go around the sun and comeback to the same place you are?
  47. H

    Accelerating a satellite in a circular orbit

    Hello, I will be thankful if you could explain what appears to me as a paradox. We know that a satellite on a circular orbit, let say around the earth, has a uniform speed given by v=√(GM/r0). Now I would like to accelerate the satellite by keeping it on the same circular orbit r0. The only...
  48. P

    I Instability of a Rigid Untethered Ring Around a Planet

    I had this discussion while driving home to California from a trip to Washington state with a friend. We were discussing the stability of a completely rigid, untethered, ring-structure around Earth, and I did not know how to explain to him that such a thing must be tethered by rigid towers lest...
  49. J

    Can you change a planet's orbit by reducing its velocity?

    My question is, take Mars, say, and install a huge rocket engine on the ground pointing out the planet (obviously) and in the opposite direction of its velocity, so that if it is turned on, the planet is slowed. The rocket starts to work and Mars is slowed. If the loss of velocity goes little by...
  50. V

    Calulate the distance of objects in Earth's orbit

    Homework Statement I am working on a report dealing with the velocity and acceleration of objects in Earth's surface based on distance from the Earth and thus far I have used the orbital speed equation and the acceleration equation. To get dive deeper into the math I would like to attempt to...
Back
Top