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.

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  1. JJBladester

    What is Pluto's speed at the most distant point in its orbit?

    Homework Statement Pluto moves in a fairly elliptical orbit around the sun. Pluto's speed at its closest approach of 4.43x109km is 6.12km/s. What is Pluto's speed at the most distant point in its orbit, where it is 7.30x109km from the sun? Homework Equations Conservation of energy...
  2. H

    Solving Spin-Orbit Coupling in Hydrogen & Li+2

    Homework Statement One of the n=5 states of hydrogen is split by spin-orbit coupling into two levels with an energy difference of 0.0039 cm^-1 . Determine the 'l' quantum number for this state and predict the analogous splitting for doubly ionised Li . Homework Equations The fine...
  3. W

    Energy required to transfer an object to a higher orbit

    Homework Statement A spaceship of mass m circles a planet (mass = M) in an orbit of radius R. How much energy is required to transfer the spaceship to a circular orbit of radius 3R? Homework Equations K=.5mv^{2} U_{g}=-\frac{GMm}{r} v=2(pi)r/T v=(ar)^.5 The Attempt at a Solution I...
  4. K

    The radius of an electron orbit in helium

    can someone explain how bohr used the mass of the nucleus in helium to develop a ratio of 4.0016 of the original rydberg constant for hydrogen? I can't seem to find the proof anywhere, I read vaguely that he found this value by calculating the increased charge in the nucleus and using the mass...
  5. M

    Sun’s contribution to total orbital angular momentum of Sun-Jupiter orbit

    From Carroll and Ostlie “An Introduction to Modern Astrophysics” prob 2.6 b After determining angular momentum of sun-jupiter orbit system in part a, the question then asks you “What contribution does the sun make toward the total orbital angular momentum. It says assume Jupiter is in a...
  6. P

    Energy required to move an object in orbit?

    The International Space Station, with a mass of 370,000 kg, is orbiting the Earth at a height 335 km and needs to be boosted to an orbit of 352 km. Calculate the energy needed to boost the ISS to its new height. m = 370,000 kg M = 5.98 x 10^24 kg G = 6.67 x 10^-11 Nm^2/kg^2 Initial...
  7. N

    How to calculate the orbit of a minor planet?

    Hello all: I'm interested in minor planet.Could you tell me how to calculate the orbit of a minor planet accurately? Is there any software to calculate it? And how to get the latest information of the minor planets?Any websites of famous international institutes who observe and...
  8. J

    What Causes Pluto's Elliptical Orbit Around the Sun?

    I understand that planets orbit follows a curve in spacetime created by the sun. Most of the planets follow the curve with seemingly a consistent radius. However Pluto follows an ellipse around the sun an appears to be inconsistent with the curve in spacetime created by the sun. Apologies if...
  9. R

    Will the Moon escape Earth's orbit in billions of years?

    I've heard that the moon is very slowly moving away from Earth. Will it eventually escape Earth's orbit?
  10. B

    Calculating Centripetal Force for a Bull in Orbit

    http://www.science27.com/forum/coworbit.jpg How much relative stronger force would it require to keep a bull in orbit when the radius was 4 times shorter. And how can this are calculated...? (The bull only wants to move straight ahead , weight and speed is the same) 4 times ? 2...
  11. R

    Satellite moving in a stable circular orbit

    Homework Statement A 600kg satellite moving in a stable circular orbit about the Earth at a height of 4000km (G=6.67x10^-11 NM^2/kg^2, Re=6380km, Me=5.98x10^24kg). Calculate the speed of the satellite at that height. Calculate the orbital period (T), the time for one revolution Calculate...
  12. B

    Energy required to the Moons orbit

    How much energy would it require (per second or per orbit) to keep the moon in orbit, if gravity did not exist? Pretend the gravity from Earth did not exist, and the moons still should orbit like it does. Does it exist a equation to calculate that?
  13. S

    Particles trajectory in a bound orbit.

    Homework Statement I am to find the particles trajectory to the first order of r/a knowing it to have the Yukawa potential v(r)=V_{\circ}r_{\circ}/r * e^{-r/r_{\circ}} = -k/r * e^{-r/a} Homework Equations \theta(r)= \int (1/r^{2})/\sqrt{2\mu (E-U-l^{2}/2\mu r^{2}}) dr...
  14. B

    Why does gravity cause lower orbit speed at smaller radii?

    At radius 1: Acceleration Due to Gravity (ADG) is 16 times as strong as at radius 4. The object at radius 1 has 4 times so much KE and 4 times so little time to change the course (into a continues circular orbit) hence ADG must be 4*4 times so strong, = ADG 16 at radius 1,- to keep the...
  15. C

    Orbital Velocity of Equatorial Satellite at 352,000 km

    Homework Statement An Earth's satelite is in equatorial orbit at 352,000 km above earth. What is the orbital velocity (m/s) of the satelite (4 sig figs) Homework Equations g1d1^2=g2d2^2 to find gravity at the height of the satellite The Attempt at a Solution I don't really know...
  16. O

    How Do You Calculate the Mass of a Star Based on Its Planet's Orbit?

    Homework Statement A distant star has a single planet circling it in a circular orbit of radius 3.33 × 1011 m. The period of the planet’s motion about the star is 836 days. What is the mass of the star? The value of the universal gravitational constant is 6.67259 × 10−11 N · m2/kg2...
  17. H

    Earth's Magnetic Field with Electron orbit

    Homework Statement High above the surface of the Earth, charged particles (such as electrons and protons) can become trapped in the Earth's magnetic field in regions known as Van Allen belts. A typical electron in a Van Allen belt has an energy of 55 keV and travels in a roughly circular orbit...
  18. J

    Help me put this rocket into orbit Need a jumpstart

    Homework Statement Ok so i had all of this typed up and some work typed out and then the page refreshed and i lost it all so this one is going to be shorter and more brief. I have to create a spreadsheet and graph of altitude vs time and speed vs altitude. My goal is to place a rocket into a...
  19. K

    Angular Momentum Conservation in Planetary Orbits

    If you were to measure the area of a sector that a planet would sweep out in one week around the sun. It would be the same no matter what time of the year it was. What conservation principle is this example demonstrating? Linear, angular or both? and why?
  20. C

    Question about the orbit between Mars and Earth

    Hallo, i have a question here, hope someone can answer it. :) As we know, two object attract each other. The closer the object, the stronger the force of attraction. This explain why Earth is attract by sun, but moon is attract by earth. (i guess.) But here i got a question, we know that...
  21. stevebd1

    Kerr Black Hole & Keplerian Stable Orbit

    The following is the equation for a Keplerian stable orbit at the equator around a Kerr black hole- \tag{1}v_s=\frac{\pm\sqrt{M}(r^2\mp2a\sqrt{Mr}+a^2 )}{\sqrt{\Delta}(r^{3/2}\pm a\sqrt{M})} where M=Gm/c^2,\ a=J/mc and \Delta=r^2-2Mr+a^2 which for a static black hole would reduce to -...
  22. F

    Horizontal velocity required to launch into orbit?

    At what horizontal velocity would a satellite have to be launched from the top of Mt. Everest (elevation 8848 m) to be placed in a circular orbit around Earth? I'm not sure where I'd start here, any tips?
  23. M

    How to much mass does it take to change Neptune's Orbit?

    Every time Neptune scatters bodies to Jupiter, Neptune gains energy and its orbit becomes larger. How much mass would Neptune have to scatter to Jupiter for Neptune’s orbit to have changed from a circular orbit at 22AU to a circular orbit at 30AU? Give the answer in terms of Neptune’s mass...
  24. C

    Elliptical Orbit Homework: Calculate r1/r0

    Homework Statement The equation of the elliptical orbit of Earth around the sun in polar coordinates is given by r =ep/1 − e cosa where p is some positive constant and e = 1/60. Let r0 and r1 denote the nearest and the furthest distance of the Earth from the sun. Calculate r1/r0...
  25. Y

    Coriolis from our orbit around the Sun

    Can we detect any coriolis forces induced from our circular orbit around the Sun ? We're going in a big circle so we should be able to detect some coriolis if we deviate from that circle - ie if we move around a bit instead of following a perfect circular path. Considering the Earth is...
  26. O

    Proving Elliptic Orbit with Rotational Matrices

    Homework Statement Prove that: r=a(cos E-e)(ihat,xi)+(sqrt(a*p)) *sin E (ihat,eta) Homework Equations E=eccentric anomaly e=eccentricity The Attempt at a Solution Rotational matrices come into play here, but I'm not sure to what extent. alpha=beta*gamma*delta, with their...
  27. V

    Abstract Algebra - Orbit of a permutation

    For this problem, I have to find all orbits of given permutation. \sigma: \mathbb{Z} \rightarrow \mathbb{Z} Where, \sigma(n)=n-3 Now, the problem is I do not know how to approach this permutation in the given format. All the permutations I dealt with were in the form: \mu...
  28. C

    Calculating Halley's Comet Orbit Eccentricity & Semi-Major Axis

    Homework Statement Consider Comet Halley. At a particular instant in time, its position and velocity are given below, in units of AU and AU/yr relative to the centre of the Sun. (x,y,z) = 0.331060, -0.455488, 0.166180) (vx,vy,vz) = (-9.01154, -7.02645, -1.30645) There are a number...
  29. Philosophaie

    Planet's Julian Date of a point in orbit

    I would like to know the Earth Date or Julian Date of the Periapsis, Vernal Equinox or any other point in the orbit for every planet in the solar system excluding Earth.
  30. G

    Maximum distance in orbit from center of a planet

    Homework Statement Consider a spherical, nonrotating planet of mass M, and radius R, with no atmosphere. A satellite is fired from the surface of the planet with speed v0 at 45o from the local vertical. In its subsequent orbit the satellite reaches a maximum distance of 5R/3 from the centre...
  31. W

    How Long Does Moon E Take to Orbit Planet?

    Homework Statement Two moons orbit a planet in nearly circular orbits. Moon D has orbital radius r, and moon E has orbital radius 4r. Moon D takes 20 days to complete one orbit. How long does it take for moon E to complete one orbit Homework Equations None - I think The Attempt...
  32. W

    Calculating Altitude in Geostationary Orbit

    Homework Statement A 10,000 kg satellite is rbiting the Earth in a geostationary orbit. The height of the satellite above the surface of the Earth is ? Homework Equations V = \omega r Newtons gravitational force equation Keplers third law equation The Attempt at a...
  33. S

    Why do planets of our solar system orbit in rings not spheres?

    I was looking at this link: http://en.wikipedia.org/wiki/File:Universe_Reference_Map_%28Location%29_001.jpeg" and wondered to myself why the asteroid belt just outside of Mars is a ring...as opposed to a sphere. Then I thought, why do all the planets seem to orbit the sun on a similar plane...
  34. G

    How Do You Solve Orbit Equations to Derive Kepler's Third Law?

    Hi, i need to solve the orbit equations that leads to Kepler's third law. The equations are : l = r * [e * cos(theta - theta0) - 1] and l = r * [e * cos(theta - theta0) + 1] where l = (J * J) / (m * k)
  35. O

    Polar Orbit Change and Line of Sight Time

    Homework Statement A satellite is in a circular polar orbit 240 km altitude. When the satellite is over the South Pole the engine is fired to achieve a polar orbit that has apogee directly over the North Pole. After the impulsive burn an observer on the North Pole observes the satellite has...
  36. C

    Bijection between Orbit and Stabilizer

    So I know this is the orbit-stabilizer theorem. I saw it in Hungerford's Algebra (but without that name). So we want to form a bijection between the right cosets of the stabilizers and the orbit. Could I define the bijection as this: f: gG/Gx--->gx Where H=G/Gx f(hx)=gx h in H ^ Is that...
  37. O

    Calculate Delta V for Lunar Orbit Transfer in 2 Maneuver Sequence

    Homework Statement A spacecraft is inserted into a lunar orbit. It varied from 101.5 km to 11,741,8 km above the surface of the moon. Later it was transferred into a circular orbit 96.6 km above the moon. Compute the delta v total for a 2 maneuver sequence to transfer the spacecraft...
  38. S

    Finding Density of a Planet Using Period of Orbit

    Homework Statement A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is T = 1.78 hours. What is density (mass/volume) of the planet? Assume that the planet has a uniform density.Homework Equations T^{2}=4*PI^2*r^3/G*M Density =...
  39. K

    Find force lawa from orbit equation

    Homework Statement The orbit of a particle moving on a central field is a circle passing through the origin, namely, r = r_0cos(\theta). Show that the force law is inverse fifth power. Homework Equations \frac{d^2u}{d\theta^2} + u = \frac{-mF(u^{-1})}{L^2u^2} u=r^{-1} The Attempt...
  40. E

    Velocity of a satellite in an elliptical orbit

    Homework Statement see attachment #12.106 Homework Equations V=R\sqrt{}(g/r) (for a circular orbit) where R is the radius of the Earth and r is the radius of the orbit from the center of the earth conservation of momentum for elliptical orbits: Vara=Vbrb The Attempt at a Solution...
  41. O

    Minimum velocity for GEO orbit transfer

    Homework Statement A GEO spacecraft crosses the earth’s equatorial plane when its true anomaly is 30 deg. The eccentricity of the orbit is 0.1 and its initial inclination is 5 deg with respect to the equator. What minimum velocity increment is required to transfer this GEO to an...
  42. O

    Impulsive delta v hyperbolic and elliptical orbit

    Homework Statement On July 1, 2004, the Cassini spacecraft approached Saturn with hyperbolic excess velocity 5.5 km/s to swing by the planet at the closest approach distance rp = 80,680 km. Compute the impulsive ΔV required for a maneuver performed at the closest approach to Saturn to...
  43. B

    Find mass of mars given period of moon orbit and radius of orbit

    Homework Statement Given data: A moon of Mars orbits with a period of 459 minutes. The radius of the moon's orbit is 9.4x10^6 m. What is the mass of mars? Homework Equations The Attempt at a Solution The only relevant equation I could find was Fmars on moon= (G*m1*m2)/(r2)...
  44. X

    How does an Electron 'jump' from one orbit to the other?

    Well, the question is that what happen when an electron changes orbits? if it cannot have states in between those orbits, how can it 'move through' those restricted areas? Do the go through those states? or just disappear and reappear without any time lapse, at two different places?? please...
  45. K

    Work on a magnet's circular orbit and Magnetic Flow

    Hello there! Long time no see! I've been struggling with this thing for a long time, and finally I've been able to write something down and wonder whether it is correct or not. Unluckily, I am trying to do something that may be more difficult than it seems, so I need your help. I am going...
  46. E

    Total energy of elliptical orbit

    Why is the total energy of an elliptical orbit given by: E_{tot}=\frac{-GMm}{2a} Where a=semi major axis. I agree for a circular orbit I can do the following: F_c=F_g ma_c=\frac{GMm}{r^2} \frac{v^2}{r}=\frac{GM}{r^2} v^2=\frac{GM}{r} Since the total energy also equal to the kinetic plus...
  47. D

    Comet Orbit Astrophyiscs question

    Homework Statement "Supposing that at perihelion a comet is 1 Au from the sun and its speed at that point is 200km/s( in a frame of referance in which sun is stationary). Find its mean PE and KE to one sig digit. Does it satisfy the virial theorem? Homework Equations K= .5mv^2 U=-GMm/r...
  48. E

    Spacetime, curvature, orbit, matter and reactions

    In the BBC film Einstein and Eddington, Eddington describes the theory of spacetime using a table cloth (space), a loaf of bread (sun) and a piece of fruit (a planet). The Bread is placed in the middle of the table cloth, this forms curves in the cloth. He then takes a piece of fruit and...
  49. B

    Calculating Planet Deceleration Due to Decreased Gravity

    Let say gravity suddenly decreased 10%, - for instance due to tidal friction etc... How fast would a planet decelerate? - How can this be calculated?
  50. F

    Orbit of a star in a sherical potential

    Homework Statement A star is at radius r = 10kpc with v_t=100km/s and v_r=50km/s. The spherical potential is \phi = V^2ln(r) with V=200km/s 1. what is r_min r_max? 2. Integrate the orbit numerically The Attempt at a Solution 1. at r_min and r_max v_r is 0 therefore I can write...
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