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. N

    Why do orbits become more eccentric when changing speed?

    From what I understand (and also assuming that the mass of one body is much greater than the other), if we had a body performing a circular orbit, and we put more (or less?) energy into the orbit by changing the speed of the body, the orbit will become more eccentric, i.e. elliptical. My...
  2. P

    Solving for θ in a Parabolic Orbit

    Homework Statement A comet of mass m moves in a parabolic orbit in the ecliptic plane (the plane of Earth’s orbit), so its perihelion distance ρ (its closest distance to the Sun) is less than Ro (the orbital distance of the Earth around the Sun) and occurs when θ = 0 for the comet. (The...
  3. G

    Proving a particle is moving in an elliptical orbit.

    Homework Statement A particle of mass m is acted upon by two forces. P(t) in the x direction with magnitude p(sinkt) and Q(t) acting on the line y=x with magnitude qsinkt. At t=0 it starts at (b,0,0) and velocity p/(mk) moving toward the origin. Prove the particle is in an elliptical orbit...
  4. P

    Find Aphelion of an elliptical orbit given Perihelion and Orbital Period

    Homework Statement Comet Halley approaches the Sun to within 0.570 AU, and its orbital period is 75.6 years. (AU is the symbol for astronomical unit, where 1 AU = 1.50 x 1011 m is the mean Earth‐Sun distance.) How far from the Sun will Halleyʹs comet travel before it starts its return...
  5. X

    Can a Golf Ball Orbit an Asteroid?

    Homework Statement The problem deals with a sports player being able to hit a golf ball at a speed of 92 m/s. The first part says to find the size of an asteroid that would have that speed as an escape velocity. The second part says that if he hits the ball at 80 m/s, what will the...
  6. T

    Patched Conics Trajectory from Initial Orbit State

    Hi, I've got a problem here, that I'd like to discuss before trying to implement any sort of solution. Basically I've got a planetarium simulation, in which I'd like to plot a patched conic trajectory ahead of a spacecraft . The planetarium only simulates two-body gravity, and switches...
  7. A

    Why does the moon orbit the Earth, and not the other way around?

    I know it has something to do with gravitational pull, but I don't know why.
  8. A

    Why do certain objects in space orbit others?

    Is it because of their different masses?
  9. H

    Need help with transfer orbit time period

    I just don't even know where to begin. I'm not sure what formulas to use and just can't do anyhting with it. any help would be great. Thanks! Recall that your trip to Mars is accomplished by using an elliptic transfer orbit going from Earth to Mars as shown in Fig. 1. This trajectory assumes...
  10. G

    Astronomy - Hohmann Transfer Orbit

    The most efficient way to reach Mars from Earth is following the Hohmann Transfer Orbit (Wolfgang Hohmann, 1925). A spaceship must first get free of Earth (it still orbits the Sun together with Earth, at 30 km/s, at a distance of 1 AU), then it adds speed so that its aphelion (in its orbit...
  11. S

    General Relativity: Particle velocity travelling on Schwarzchild orbit

    Homework Statement What is the speed of a particle in the smallest possible circular orbit in the Schwarzschild geometry as measured by a stationary observer at that orbit? Note: The orbit in question happens to be unstable. Homework Equations Normalization condition...
  12. H

    Binary stars ,time period of orbit?

    Homework Statement A binary system consists of two stars of equal mass m orbiting each other in a circular orbit under the influence of gravitational forces. The period of the orbit is τ . At t = 0, the motion is stopped and the stars are allowed to fall towards each other. After what time t...
  13. T

    Gravitational pull on asteroid/Period it takes for one orbit

    Homework Statement A bit of asteroid material of mass 2.5 x 10^6 kg orbits around the Earth at an altitude of 2800km. How long does it take the asteroid to complete one orbit. M asteroid = 2.5 x 10^6 kg altitude of asteroid = 2800 km radius asteroid = 200m radius Earth = 6.37 x 10^6 m...
  14. F

    Does how black holes inside galaxies orbit around the central black hole tell us

    Does how black holes inside galaxies orbit around the central black hole tell us anything useful? Could be my noobness, but the idea of a bunch of black holes orbiting a central black hole just seems messy. ha. Have we got the jist of what would happen if a black hole ate another black hole? if...
  15. R

    Proving rationals cannot have dense orbit in Cantor set

    Homework Statement Let C be the standard Cantor "middle third" set (ie Ck = {x:0\leqT^{k}_{3/2}(x)\leq1} and C = \bigcap^{inf}_{k=0}Ck where T^{k}_{3/2} = 3x if x<1/2, = 3 - 3x if x \geq 1/2) Show that a rational number x = p/q \in C cannot have dense...
  16. A

    Maximum acceleration of the body in elliptic orbit.

    There was this question in the book, at which place on the elliptic orbit the body has maximum acceleration. Since acceleration is proportional to force, a = GM/r^2, this should happen when the distance r is minimum, this is when the planet is at perihelion. But the contradiction is that at...
  17. D

    Gravitational motion problem, degrees along orbit

    Homework Statement A comet passes the sun at it's perihelion 5*1010 meters going 1*105 meters/second. Take the mass of the sun to be 2*1030. a.) Will the comet return to this point? If so, how long until that happens? b.) How long will it take to travel from perihelion to 60 degrees...
  18. D

    Elliptical Orbit Homework: Momentum, Direction & d/dt

    Homework Statement Based on your observations of the behavior of your computer model of a planet orbiting a star, and on your reading in the textbook, which of the following statements about an elliptical orbit are true? At any instant the momentum of the planet is tangent to the planet's...
  19. F

    How Does Orbital Radius Change with a Time-Varying Solar Mass?

    Homework Statement An approach to the problem of finding how orbital radius changes with solar mass is to solve the radial equation of motion for a gravitational force that has an explicit time dependence based on the assumed rate of mass loss. Show by numerically solving this equation of...
  20. C

    Zeeman effect - spin orbit coupling

    As far as I know: the possible orientations that the total angular momentum can take (given my Mj) are degenerate. if we apply a magnetic field, degeneracy will be lost and different states arise. this is the zeeman effect but when looking up on google for zeeman effect, a webpage used as an...
  21. P

    Apocentre and Eccentricity of a Comet's Orbit

    Homework Statement If a comet passes close to the Earth with a velocity of 38km/s, how far is the apocentre of its orbit from the Sun? What is the eccentricity of its orbit? Homework Equations Vis-Viva Equation: (V)_{ecc}^{2} = GM [ \frac{2}{R} - \frac{1}{a} ] Apocentre distance...
  22. N

    Which Has a Greater Gravitational Pull on Earth: Sun or Moon?

    Why does the Earth orbit the Sun, but the Moon pull on Earth's tides? Earth orbits the sun, proving that the Sun has a greater gravitational pull on the Earth than the Moon. However, the Moon control's Earth's tides (unlike the Sun), which proves the opposite-the Moon has a greater...
  23. M

    Longest and shortest distance in an elliptical orbit

    Homework Statement Two satellites are launched at a distance R from a planet of negligible radius. Both satellites are launched in the tangential direction. The first satellite launches correctly at a speed v0 and enters a circular orbit. The second satellite, however, is launched at a speed...
  24. P

    Effect of Instantaneous Velocity Change on Orbit

    Homework Statement A small particle of mass m is on a circular orbit of radius R around a much larger mass M. Suppose we suddenly increase the speed at which the mass m is moving by a factor (that is, v_{final} = α * v_{initial}, with α > 1). Compute the major axis, minor axis, pericentre...
  25. J

    Energy needed to reach planets orbit and leave to leave it.

    How many TJ of energy is necessary to get a 300 ton spacecraft from the surface of Venus to 1) orbit at 60520km and 2) to leave the planets gravitational field? 12104km Venus diameter 6052 is Venus radius therefore. 4,9 * 10ˇ24 kg Venus mass 60520km orbit radius T-1,9 Earth days...
  26. K

    Orbital mechanics: Accelrating takes you into a slower orbit?

    I'm confused by something very simple and stupid. When the mass of a satellite is tiny compared to the body being orbited, we can approximate orbital velocity as sqrt{(GM)/r} Now its obvious that as r gets larger, the orbital velocity drops. Higher orbits are slower orbits. A...
  27. H

    Space station-nature of orbit?

    Homework Statement A space station moving in a circular orbit around the Earth goes into a new bound orbit by firing its engine radially outaward.This orbit is... Choices are; (a) A larger circle (b)A smaller circle (c)An ellipse (d)a parabola Homework Equations The Attempt at...
  28. S

    Calculating the period of an orbit

    If I have all six orbital elements, what equations allow me to calculate the period of the object?
  29. B

    Understanding Electron Orbits: A Physics Problem Explained

    Here is a problem from a physics text An electron (mass 9.11 × 10−31 kg) orbits a hydrogen nucleus at a radius of 5.3 × 10−11 m at a speed of 2.2 × 106 m/s. Find the centripetal force acting on the electron. What type of force supplies the centripetal force? I'm not interested in the...
  30. A

    Orbit to the Moon: nodes position

    Hi everybody, I'm planning a 2016 mission to the moon similar to Apollo 8 (Orbital mechanics homework). I decided to start from a equatorial parking orbit, and then to perform a plane change. The problem is that I obviously need to know the position of the moon's orbit plane, which, as you know...
  31. P

    Spin and orbit velocity of electron slows down approaching c ?

    Spin and orbit velocity of electron slows down approaching "c"? If happen a atom to get very close the velocity "c" the time will almost stop. What will happen to the velocity of the orbit and spin of a electron? It will slow down too?
  32. W

    Position of a Body on a Hyperbolic/Parabolic Orbit with Respect to Time

    .. Using Keplerian Elements Hi. Disclaimer: this is the first foray into orbits I've ever taken. I only did mechanics in university and haven't really touched it sincew. I'm busy coding a simulation of a solar system. I've managed to code a routine to calculate the position of a body along...
  33. brainpushups

    Bound Orbit (numerical solution)

    Homework Statement Consider a particle with mass m and angular momentum l in the field of a central force F=\frac{-k}{r^{5/2}}. To simplify your equations, choose units for which m=l=k=1. a) find the value r_{0} of r at which U_{eff} is a minimum and make a plot of U_{eff}(r) for 0<r<5r_{0}...
  34. H

    Orbit of Moon and the earth around thier COM

    Homework Statement does the moon orbit the Earth or the Center of mass of the earth-moon system. 2. Relevant ideas well, i think that it orbits the COM of the earth-moon system. If this is the case then is the radius of the moon from the Earth always constant. ie, if the moon...
  35. M

    Impact & Gravitational Effects of Asteroids/Comets on Moons Orbit

    How big would an asteroid or comet need to be to say, disturb the moons orbit, either by impact or gravitational attraction? And would this significantly alter the chances of "Death From Above"? :)
  36. M

    Location of minimum change in velocity for orbit escape

    Homework Statement A rocket is in elliptic orbit about the earth. To put it into escape velocity, its engine is fired briefly, changing the rocket’s velocity by deltaV . Where in the orbit, and in what direction, should the firing occur to attain escape with a minimum value of deltav...
  37. U

    Object In Orbit pushed by a velocity and crashes onto moon.

    Homework Statement I attached the problem to this post. I need help on the second question and I need to turn it in tomorrow. I'm not sure if I'm supposed to use anything from the first as they are both related. Homework Equations U + KE rvsinθ = rvsinθ These are all the equations...
  38. S

    Computation of Solar Position and Velocity Vectors (Meteor Orbit)

    I'm looking at some code from a book that details uses the heliocentric position and velocity to compute an orbit of a meteor. See attached pages. At the top of the section at mid-page, page 37, he gives a source, Herget, 1953, Solar Coordinates 1800-2000. The book was written in the...
  39. J

    First post ever. Be Kind. Solar orbit questions

    Hello, total layman here. I have some questions & ideas, but no one to discuss them with, so here I am. 1. In the continuum between a completely circular orbit, and a maximally elliptical orbit, what characteristics of the orbital body and the gravitational source are the prime determinants...
  40. T

    Intensity of solar radiation at earth orbit

    Homework Statement I am try to understand how the value of 1370 watts per metre squared for the intensity of sunlight hitting the Earth has been derived. Is there a way to see this mathematically? Homework Equations I understand about how the intensity is related to Poyntings vector, by...
  41. K

    What is the period of the ISS orbit?

    Homework Statement The International Space Station (ISS) circles the Earth at an altitude of 347 km. What is the period of the orbit of the ISS expressed in minutes? G=6.67x10^-11 N * m^2 /kg^2 M(Earth)=5.98*10^24 kg Homework Equations T^2/R^3 = (4Pi^2)/(GM) So: T^2=...
  42. M

    Centripetal acceleration of an orbit to the earth help

    Homework Statement A geostationary satellite goes around the Earth in 24hr. Thus, it appears motionless in the sky and is a valuable component for telecommunications, including digital television. If such a satellite is in orbit around the Earth at an altitude of 35 800 km above the Earth's...
  43. M

    How much energy is required to move this satellite to a circular orbit

    Homework Statement How much energy is required to move this satellite to a circular orbit with a radius of 2.50×104 miles? I've found the answer to Part A of this problem to be 1.59*10^10, if this helps solve the above^^ (Find the kinetic energy of a 1.80×103 kg satellite in a circular...
  44. M

    Calculating the Mass of the Sun Using Earth's Orbit Data

    The Earth orbits the sun in an approximately circular orbit of radius 1.496 * 10^11 m (about 93 million miles) in a period of 365 days. Use these data to determine the mass of the sun. Solution: F = (Ms)(Me)(G)/r^2 I have two unknowns... F and Ms... please give suggestions because I...
  45. xaratustra

    Landau quantization of cyclotron orbit

    I don't know what the speed of light c is doing in the Hamiltonian for the Landau quantization. The term doesn't have dimensions of momentum anymore. :confused: \hat{H}=\dfrac{\hat{p}^2_x}{2m}+\dfrac{1}{2m}\left(\hat{p}_y-\dfrac{q|\vec{B}|}{c}\hat{x}\right)^2 Any ideas? thanks.
  46. D

    Calculating Kinetic & Potential Energy of a Bohr Orbit

    Homework Statement A particular Bohr orbit in a hydrogen atom has a total energy of -0.85eV. What are (i) the kinetic energy of the electron in this orbit, and (ii) the electric potential energy of teh system? Homework Equations E=mc^2 KE= 1/2mv^2 E = hc/lambda The Attempt...
  47. K

    Work done by a force changing the distance of a satellite's orbit

    Homework Statement A 5530-kg satellite is in a circular Earth orbit that has a radius of 1.81 × 10^7 m. A net external force must act on the satellite to make it change to a circular orbit that has a radius of 8.01 × 10^6 m. What work must the net external force do? Homework Equations...
  48. B

    Circular Motion - Spacecraft in Orbit

    Homework Statement A spacecraft moves in a circular orbit with a speed of 7.60E+0 km/s with a period of 95.1 min. What is the radius of the spacecraft 's orbit? My answer, which is correct, is 6.90×106 m What is the radial acceleration of the satellite? 8.37 m/s^2 was my answer, and it...
  49. K

    How to simulate planets orbit curce around the sun ?

    How to simulate planets orbit curve around the sun ? Hi I'm about to write a java program where I wish to simulate planets orbit curve around the sun, so that I can set the speed of a planet and mass of planet and sun and simulate the curves around the sun (just basic simulations). I only...
  50. T

    Find minimum energy to escape an orbit

    Homework Statement When it orbited the Moon, the Apollo 11 spacecraft ’s mass was 7170 kg, its period was 121 min, and its mean distance from the Moon’s center was 1.87167 × 106 m. Assume its orbit was circular and the Moon to be a uniform sphere of mass 7.36 ×1022 kg. Its orbital speed was...
Back
Top