# What is Planetary orbits: Definition and 34 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. ### I Would there be any way to avoid gravitational wave emissions?

In principle every object orbiting another (e.g. a planet revolving around a star) would emit gravitational waves, relaxing the orbit over time.However, this would not happen if the orbits had a time-invariant and symmetric quadrupole moment. As it is indicated in this question (), it appears...
2. ### Solar System Forces -- Simulating the planetary orbits for my project

TL;DR Summary: Solar sytem forces on Unity Hello ! For my last year in my school, I've got a project to do, and I wanted to recreate the Solar system with forces on Unity. My forces are Velocity and Acceleration (I'm using the Frenet's formulas). I'm sorry I'm not a physicist and that's why...
3. ### A N-Body Simulations of Chaos in the Orbits of Trappist System Planets

As a retired physics professor with a long experience in complex simulation software for high energy physics experiments (e.g. the LHC) I revisited last July the n-body planetary simulations which I taught in an undergraduate physics course during the Spring 2017. It was then that the...
4. ### B Planetary Orbits - Elliptical or Wavelike?

I was running a simulation in Universe Sandbox where I placed a 10 million solar mass black hole about 10 light years from the Solar System, initially stationary relative to the Sun. I noticed once the Sun had reached about 70km/s relative to the black hole, all the orbits became wavelike rather...
5. ### I The centripetal acceleration of the planets in our solar system

Relevant formulae:- Angular velocity in uniform circular motion ##=## ##\omega## ##=## ##\frac {2\pi} t##, where ##t## is the time taken to complete one revolution. Centripetal acceleration in uniform circular motion ##=## ##a## ##=## ##\omega^2r##, where ##r## is the radius of the circular...
6. ### I Planetary orbits - the 2-body problem

Hi I am confused about certain aspects of deriving the planetary orbit equation by considering it as 2-body problem. I will ask my first question now before i get to my other questions. In the David Tong notes on "Dynamics & Relativity" he states that a particle in central force potential...
7. ### Stargazing Planetary orbits -- Why do planets orbit at same “level”?

Why is it that all of the planets in our solar system (to our knowledge) orbit the sun in such a way that they all go around the sun in roughly similar orbital planes? Why don’t we have planets with orbital planes at significantly different angles?
8. ### I Exploring Planetary Orbits and the Sun's Rotation

Are there any good theories which can explain how the orbits of planets are not aligned with the rotation of the Sun? I gather there is about 6 degrees of differance, which is not small.
9. ### Push Mercury out to Venus' orbit?

So it would be cooler and mine-able? Given unlimited tech and wealth in a fictional setting.
10. ### B Enlarging Planetary Orbits: Evidence of the Solar System's Evolution?

Is there any evidence of the enlargement of planetary orbits over time? Are the planets moving further from the sun?
11. ### I Planetary Orbits: Force needed for circular orbit

Hi! first time poster here. I'm making an orbital simulation and I am having a problem with one minor detail. The gravity is working great, and I've programmed it using this formula: A force vector is applied = DirectionOfCentralBodyNormalized * ((GravConstant * centralbodymass *...
12. ### I Planetary Orbits in AU - Stability & Mass Limits

All of the planets should have individual orbits, and should be between the mass of Mercury and Mars. What can their orbits be in AU's? Is there a way to find out how close they can be without destabilizing each other? If we assume the star is about the same size as Sol.
13. ### Orbit of Cube Planet: Physics Explained

What is the physics behind a orbit a cube planet. Does the convential physics including keplars laws and circular motion still apply. Also The cube having a centre of mass posited in the middle of the cude does this mean it can be consider point mass and the same as spherical planet orbit? any...
14. ### Planck's constant in planetary orbits

The question is: If quantum mechanics were detectable in planetary orbits, how much larger than the currently accepted value would Plancks constant need to be? Relevant equations ΔxΔpx ≥ħ/2 p=mv Earth-Sun dist 1.496E11 Earth orbit speed 28,900ms^-1 Earth mass 5.972E24 kg The attempt at a...
15. ### Cross Section for Asteroid Impact

Homework Statement In this problem, you will estimate the cross section for an earth-asteroid collision. In all that follows, assume that the Earth is fixed in space and that the radius of the asteroid is much less than the radius R of the earth. The mass of the Earth is M_e, and the mass of...
16. ### Relativistic Orbits: Effects of Mass Increase & Length Contraction

Suppose an observer flies through our solar system at ##v \approx c## relative to the Sun, such that he sees each planet's (and the sun's) mass as greatly increased. What happens to the orbits of the planets? Since he sees the center of mass of the solar system as flying past him at ##v \approx...
17. ### Planetary Orbits & Orbital Velocity

Hi pf, please could someone explain why the orbital velocity increases as you get closer to the sun. I treated the situation like circular motion and did a load of calculations. I calculated the orbital velocity of all 8 planets and then the force between each of the eight planets and the sun. I...
18. ### Magnetic forces in planetary orbits

This suddenly entered my mind while studying magnetic fields. I know of course that it is the gravitational force that holds the planets in orbit, but do their magnetic fields also have an effect, even by an infinitesimal amount? Do the magnetic fields of the planets have a small influence on...
19. ### Is Velocity Consistent in Planetary Orbits?

Is the speed of different bodies in the same planetary orbit equal to each other? I think it should be the same because the acceleration is always the same in such a case. But it was not so when i compared the speed of moon per m/s with that of the international space station.
20. ### Planetary Orbits calculated from the Metric

I am learning about General Relativity. The planetary orbits can be calculated with more precision especially Mercury. I am stuck on how to get from the Schwarzschild Metric: a four variable Differential Equation to a radius(r,theta,phi,t) and velocity(r,theta,phi,t) of a single planet...
21. ### The Basics Regarding : Planetary Orbits and Whatnot

Q: Why is it that objects in orbit around other objects, tend to do that in elliptical patterns, and not circular patterns? I can picture objects of great mass, planets and stars warping the fabric of space time, and how moons and whatnot get caught spinning in the orbit. But can't wrap my head...
22. ### Planetary orbits in a Binary Star system.

http://spaceflightnow.com/news/n0210/11planet/ This is the only discovered planetary orbit around a close binary star that I know about. I have some general questions about planetary orbits around or within close binary systems or even the further apart binary star formations or triples...
23. ### Planetary Orbits: Decay or Spiral?

So, the moon goes around the earth, the Earth orbits the sun etc... Are the orbits eventually decaying orbits? That is, given enough time, will the moon hit the earth, Earth go into the sun etc...?? Is that why galaxies are spiralling?
24. ### Inclination of planetary orbits

Does anyone know the inclination of each planetary orbit (in degrees) with respect to the plane of the Sun's equator-plane?All planetary inclinations are known with respest to the ecliptic, and the ecliptic's inclination is known with rescpect to the Sun's equator (7.25 degrees). Such data...
25. ### What Units Should I Use to Calculate Planetary Orbit Time?

Hi all, I'm working on a problem where I have to find the time it takes for a planet to form from a protoplanetary disk, using the equation: t = \frac {3}{A}M^{1/3} Where A= ( \frac {(1+2\beta)\sigma}{P}) (\frac {3\pi^2}{4\rho_m})^{2/3} However, I'm not sure which units the...
26. ### Comparing Planetary Orbits & Rotations in Pictured Figures

I want to know the difference between the 2 types of rotations shown in the picture attached . planetary orbiting are similar to the second figure in the picture attached , all i want to know what is the difference between the 2 figures .
27. ### How Did Planets Enter Their Orbits?

This is something I thought about while drifting off to bed last night. Immediately after the period between the big bang and the formation of planets, how did these newly created planets enter their respective orbits. I'm assuming the planets had different masses and that this was a...
28. ### How does a sudden doubling of the mass of a star affect the orbit of a planet?

Suppose you have a star of mass M and a planet of mass m orbiting around it. The orbit is circular. m<<<M. U of course is -GmM/r^2. E of course is going to be -U/2 and kinetic energy U/2 due to the virial theorem. What would happen if the mass of the star suddenly doubles? This is...
29. ### Why are planetary orbits so circular?

Over in another forum I've got myself in trouble by suggesting that theoreticians haven't paid enough attention to this question. George Jones has kindlyhttps://www.physicsforums.com/showthread.php?p=2100856#post2100856" that the question seems to have been answered along the lines of...
30. ### The Mysterious Plane of Planetary Orbits

Why do the elliptical orbits of the planets in our solar system rotate on a single plane.
31. ### Why most of the planetary orbits are ellipitical?

theoretically by GMm/r^2 = mv^2/r, planets in a particular distance to the star will move in the corresponding velocity in order to maintain a circular orbit... either over speed they will pass by the star, or under speed they will be attracted towards the star in a spiral way So why are...
32. ### Effect of Sun movement on Planetary orbits?

What is the effect (if any) of the sun's movement around the galactic center in relation to planetary orbits?
33. ### Proving Pluto's Orbit Inside Neptune's - Maths Investigation

Hi guys Im currently investigating planetary orbits in maths and one of our problems is to prove that Pluto spends a good deal of its time inside the orbit of Neptune. If anyone could help that would be great. Thanks Kyle
34. ### Planetary Orbits Around Black Holes

i know that if a star having planets dies, and becomes a black hole the planets continue to revolve around the black hole. how is it possible when the black hole sucks everything??:confused: