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. Ryan Reed

    Do Spin-Orbit Interactions change the Orbital of an Electron

    Does the orbital of an electron change when it experiences a spin-orbit interaction, and if so, how?
  2. E

    Earth's Orbit & Fleming's Left Hand Rule

    Please forgive me as I am inquisitive enough to be dangerous. Question First, Thoughts Behind It: * How much validity is there in the application of Fleming's Left [edit: RIGHT!] Hand Rule towards the orbit of the Earth around the Sun? * I saw that NASA recognizes this but they seem to sort...
  3. J-dizzal

    Planets and satellites, law of periods circular orbit.

    Homework Statement A 15 kg satellite has a circular orbit with a period of 4.4 h and a radius of 3.5 × 106 m around a planet of unknown mass. If the magnitude of the gravitational acceleration on the surface of the planet is 1.2 m/s2, what is the radius of the planet? Homework EquationsThe...
  4. L

    Gravitation - Changing Orbit Dynamics

    Homework Statement A spaceship is in a circular orbit of radius ##r_0## about a planet of mass M. A brief but intense firing of its engine in the forward direction decreases the spaceship's speed by 50%. This causes the spaceship to move into an elliptical orbit. a) What is the spaceship's...
  5. P

    Why is black hole photon sphere outside the event horizon?

    Homework Statement I am preparing a report on black holes and I recently learned about a phenomenon I was previously unaware of: the photon sphere of a black hole. While reading an article on said occurrence (I have now confirmed this on multiple sources) the photon sphere which is the minimum...
  6. avito009

    Why does the moon orbit the sun?

    I know that Earth orbits the sun because it has initial momentum and that prevents it from falling into the sun. But does moon that orbits the Earth also have initial momentum?
  7. H

    Understanding the Fixed Energy of Electrons in Bohr's Orbit

    After Doing lot of research, I still am Unable To Understand, How a Electron in Fixed orbit (with fixed energy) is not radiating energy as it is continuously accelerating. According to my Book, Rutherford only missed "Fixed orbit" word in his theory? Moreover, Speed of electron is described as...
  8. Mazin Nasralla

    Venus Transit - What should be a simple problem

    I was given a question which I have worked out, but not to my satisfaction... "if the inclination of Earth and Venus orbit was the same, how often would the transit occur?" I am given 4 options and I have got the right answer, but I did it by trial and error, and I am sure that there must be a...
  9. A

    Solar System barycenter - Orbit of planets

    Hi As far as I know the Earth orbits around the Sun Earth barycenter while the Sun orbits the Solar System BaryCenter formed by the changing center of mass of the Solar system. So even while the Sun orbits the SSBC and Earth orbits the Sun-Earth BC it would not be true to say the Earth...
  10. davenn

    Pluto's moon Nix and its wild tumbling orbit

    Note the explanation text below the videocheers Dave
  11. Jireat

    Why do small bodies stay in orbit around large bodies?

    I know this sounds like an elementary question with an easy answer. However, I was thinking about chaos theory. Planets and stars are always changing so that their gravitational pulls towards other objects varies. Shouldn't the tiniest change between the pull of a star and a planet, or a planet...
  12. MelkoRR

    Calculation of a comet orbiting Sun

    Homework Statement a comet is orbiting around the Sun in a parabolic orbit . center of the sun to perigee of the comet's orbit distance is 58 km . find the time required for the comet to transit into the Earth orbit around the sun . Homework Equations The Attempt at a Solution no clue
  13. M

    Comet on a parabolic orbit around the Sun

    Homework Statement given: the speed at perihelion What is comets full energy? What is its distance from Sun at perihelion? How much time is the comet located inside Earth's orbit? Homework Equations parabolic orbit equation 3. The attempt at a solutin wrongly calculated l
  14. RisingSun361

    Is it theoretically possible for a star to orbit a planet?

    I was doing some research on the findings of the Kepler space telescope this morning. I noticed that some of the stars it has found are quite small, and some of the planets in other systems are quite large. Is it theoretically possible for there to be a situation somewhere in the universe where...
  15. T

    Is Tidal Circularisation of Orbits a Tricky Concept?

    Homework Statement A body on an orbit with semi-major axis a and eccentricity e undergoes tidal circularisation. Show that the orbit will circularise at a semi-major axis, acirc, given by acirc = 2rperi = 2a (1 − e). Homework Equations No equations given, but I think the following could...
  16. P

    Orbital Rendezvous and Mission Control Involvement

    Can someone please give a step by step explanation of an orbital rendezvous by a spacecraft for a target that is orbiting the body it launched from? And if possible, can you explain how mission control is involved and what part computers play? When the RCS is active is it changing the...
  17. U

    Satellite orbiting around Earth - Spacetime Metric

    Homework Statement The metric near Earth is ##ds^2 = -c^2 \left(1-\frac{2GM}{rc^2} \right)dt^2 + \left(1+\frac{2GM}{rc^2} \right)\left( dx^2+dy^2+dz^2\right)##. (a) Find all non-zero christoffel symbols for this metric. (b) Find satellite's period. (c) Why does ##R^i_{0j0} \simeq \partial_j...
  18. Bucho

    Orbit of Geostationary Satellites

    Hi all, I feel like I have the answer, or am at least in the ballpark, but I'm not confident in this area and so I also feel like there should be a more concise, or "beautiful" way to express it. Am I missing something? 1. Homework Statement Explain why the orbit of a geostationary satellite...
  19. L

    What Are the Calculations for the Orbit of Vanguard 1 Satellite?

    So for an online quiz, I am stuck on this question: The oldest artificial satellite still in orbit is Vanguard I, launched March 3, 1958. Its mass is 1.60 kg. Neglecting atmospheric drag, the satellite would still be in its initial orbit, with a minimum distance from the center of the Earth of...
  20. P

    Direction of Burn while in Orbit

    I know that when a spacecraft is in orbit, the direction in which the spacecraft produces thrust affects its orbit. If the thrust is tangent to the orbit, the orbit's shape (eccentricity and size) changes. If the thrust is perpendicular to the orbit, but tangent to the surface of the...
  21. A

    Euler's Method and Planetary Motion

    Homework Statement Hi there, I wish to use Newton's Laws in conjunction with Euler's Method to model the motion of a planet around a star.Homework Equations 2nd Law F = m*a Law of Universal Gravitation F = -G*M1*M2/r^2 The Attempt at a Solution [/B] First I combined the two laws above...
  22. K

    Can we distinguish between black holes and white holes?

    I know white holes probably don't exist, but I'm having trouble understanding how someone outside the white hole would perceive them. My understanding is that they are time-reversed black holes. I've read that nothing can fall into a white hole, that it is repulsive, and that it continually...
  23. AndrewC

    Closest stable orbit of a body around earth

    Homework Statement This is a problem I picked for my calculus one class that I would like to solve, then model the solution using the sandbox video game universe sandbox. I would like to calculate the closest stable orbit of the moon, if possible allowing for some eccentricity in the orbit...
  24. T

    Two moons in tidal lock orbit: phases, tides, axial tilt?

    Consider the following; We have Earth with two moons in orbit (discounting the existence of our own moon for the sake of this hypothetical scenario). One moon is the size and mass of Pluto, orbiting around 70,000km from Earth. The other is the size and mass of Pluto's moon, Charon, orbiting...
  25. D

    How can I calculate velocity of planet using orbit time?

    Hi. I'm just a hobbier of astronomy and have a question about elliptical orbit. In Before, I had calculated the elipse of a planet successfully. In this case, I wonder that can calculate velocity(red vector) using orbit time(or position on elipse). Let me assume that we know orbit's semi-major...
  26. Calpalned

    Two equal-mass stars orbit each other

    Homework Statement Two equal-mass stars maintain a constant distance apart of ## 8.0 *(10^11) ## m it is eight times ten to the eleventh, not eight times ten to the first power times one. I don't know why Latex forbids exponents of two digits or more and rotate about a point midway between...
  27. samjohnny

    Mastering Perturbations in Near Circular Orbits: A Comprehensive Guide

    Homework Statement Attached. Homework Equations The Attempt at a Solution Hi. This question has me really puzzled; I simply don't know where to start with this one and thus am not sure of any relevant equations. It seems to be a problem about small perturbations to the circular...
  28. P

    Investigating Comet 67P's Elliptical Orbit

    Homework Statement Currently, I am trying to prove the "conservation of energy" concept within a comet's elliptical orbit by finding the mechanical energy of the aphelion and perihelion point to see if they're equal. However, they don't equal each other when I calculate both points. (aphelion...
  29. D

    Calculate elliptical orbit using attitude and velocity

    Hi. I'm just a hobbier of astronomy and have a question about elliptical orbit. I wonder that can calculate elliptical orbit using just atitude(location) and velocity(vector). Please look at my picture. The blue dot is central body and green dot is my interesting body. Let me assume mass of...
  30. P

    Perturbed circular orbit under central force motion?

    I am self studying Kleppner and Kolenkow's an Introduction to mechanics. But i have one doubt about how they got into the equation no 3 of the example problem 9.3 in Central Force Motion. Please clarify my doubt.
  31. S

    Fitting an ellipse through 3-d data

    Hey, sorry if this is not the right section to post in, the topic is a bit ambiguous. I've generated a set of coordinate points for the orbit of Mercury (3d cartesian) and now I want to fit an ellipse through it so I can get an accurate estimate of the location of the perihelion. I am using...
  32. MisterAmrani

    Seasons due to Earth's elliptical orbit

    Hello there! What I have never understood is that our seasons are the result of the tilt of the Earth's axis, and I've always interpreted that to mean that the northern hemisphere is closer to the sun in June, July, and August, and the southern in December, January, and February. If that is the...
  33. nmsurobert

    Electron acceleration in its lowest orbit

    Homework Statement Calculate the centripetal acceleration of an electron in the lowest Bohr orbit. Homework Equations no equations were given but i think i have to use ac = v2/r were v = 2.19 x 106 m/s (speed of electron in its lowest orbit) r = ao = 5.29 x 10-11m (minimum radius) The Attempt...
  34. G

    Relationship between characteristic energy and delta-v

    Firstly, apologies if this is in the wrong thread. I'm currently writing a presentation on the physics of getting a spacecraft from Earth to Mars in the near future. In my research I've come up against Porkchop plots which seem to plot contours of equal characteristic energy so you can find...
  35. T

    Calculate time (or fraction of orb. period) of sat. in umbra

    Greetings! I would like to know how to calculate the time, or fraction of orbital period, that a satellite spends in umbra? (total solar eclipse for satellite when they aren't affected by Solar radiation pressure and solar panels don't generate power). Information given would be satellite's...
  36. U

    General Relativity - Circular Orbit around Earth

    Homework Statement (a) Find the proper time in the rest frame of particle (b) Find the proper time in the laboratory frame (c) Find the proper time in a photon that travels from A to B in time P Homework EquationsThe Attempt at a Solution Part(a) [/B] The metric is given by: ds^2 =...
  37. 2

    How can you tell what kind of orbit a body will have?

    Is there a way of telling whether the orbit of a body around another, or rather of both around their centre of mass, will give the object in question a circular, elliptical, hyperbolic or parabolic orbit? Thank you!
  38. Suraj M

    Gravity and velocity of a body in an elliptical orbit

    consider a body revolving around a star and having a velocity v when closest to the star ( distance r) then the velocity of the body at a point farthest ( distance R) is? 1)by angular momentum conservation :: r × mv = R× mV »V = (r/R).v...
  39. D

    Stability of Orbital Resonance Ratios

    I was looking at some interesting resonant orbits in our solar system and was wondering if someone who knows a lot more about planetary orbits than I might be able to answer if a certain scenario would actually lead to stable orbits or not. The scenario I have in mind is four planets tightly...
  40. marcus

    I Dawn dead in Ceres orbit, ran out of fuel Oct 2018

    Published on Jan 19, 2015 The Dawn spacecraft observed Ceres for an hour on Jan. 13, 2015, from a distance of 238,000 miles (383,000 kilometres). A little more than half of its surface was observed at a resolution of 27 pixels. This video shows bright and dark features. This video was created...
  41. A

    Is the Circular Orbit in a Multi-Electron Atom Stable?

    Homework Statement In a classical model of a multi-electron atom, electrons are assumed to move in a modified electrostatic potential $V(r)$, given by; $$V(r)=\dfrac{-k}{r}e^{-r/a}$$ Show that the effective potential is ; $$V_e(r)=\dfrac{J^2}{2mr^2}+\dfrac{-k}{r}e^{-r/a}$$ Then show that...
  42. James William

    Planetary orbit disruption by passing stars

    I read this interesting paper showing that in less than a million years, one star will fly past our Sun at a distance of about 0.13 light years [1]. How might I calculate the maximum disruption this could cause on the orbit of an object in orbit around our Sun, such as planets and comets...
  43. H

    How to treat spin orbit operator directly

    For an electron the spin operator S_zis represented by a 2×2 matrix, with spin up and down as its bases. Consider the angular momentum operator L_z with l=1 which is a 3×3 matrix. How can we treat the L_z S_z operator directly in matrix form?
  44. N

    How do electrons orbit the nucleus?

    I have heard that instead of orbiting the nucleus they actually pop into and out of existence around the nucleus forming the electron cloud, and where they relocate depends on the probability of that area due to wave function, am i right?
  45. O

    What force classically held electron in the orbit?

    Hey, what force classically held electron in the orbit? Also what force is it actually (quantum mechanics). I think it was the electromagnetic force classically, I haven't been able to find a legit source that says it was directly that, but when I do calculations with electrons and atoms I'm...
  46. L

    Centripetal acceleration of objects in orbit around the Earth

    Hi all. The answer to this might be trivial. If it is, sorry for posting. If you calculate the acceleration due to gravity of an orbiting satellite, it could be around 8.5-9.5m.s-2, depending. So, it's tangential velocity is such that as it falls towards earth, Earth curves away and the...
  47. D

    Satellite Energy and Orbit problem

    Homework Statement A spy satellite of mass m is in a circular orbit with radius R and velocity v around the earth. One of the satellites thrusters suddenly fires giving it an additional velocity v in the outward radial direction (same v). What is the new total energy of the satellite? What is...
  48. mrspeedybob

    Why did the Apollo spacecraft go into Earth orbit first?

    I've been playing Kerbal Space Program. I have found the simplest way to get to an outer planet is to launch straight up at dawn and the simplest way to get to an inner planet is to launch straight up at dusk, and in neither case to mess about with going into Kerbal orbit. This got me to...
  49. C

    What is the value of k in the Moon's orbital precession?

    I want to compute the precession of the Moon's orbital plane, sometimes called as the precession of nodes. I assume simple harmonic motion; the Moon orbit lies in a plane X-Y, so it oscillates along z: z'' = -kz By definition k = w^2; and we know already: w = 2pi/18.6y; because the period of...
  50. T

    Difference between orbital mechanics and astrodynamics ?

    Hello all. The title of this thread sums up my question - what is the difference between orbital mechanics and astrodynamics ? Or is there a difference at all ? I have sometimes seen different uses of the terms, for example, on many sites I see " astrodynamics or orbital mechanics is ... " ...
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