What is Orbits: Definition and 497 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. R

    Calculating Orbits of Groups: SO(3)

    group theory : orbits hi. I'm trying to calculate the orbits of some simple groups. I have found many explanations of what they are, but no example calculations. does anyone have any ideas where to look. I'm trying to calculate the orbit of SO(3). thanks
  2. H

    How is potential energy related to orbits of satellites?

    Hi! I really don't even understand what this problem is talking about! If someone could just point me in the right direction, I would appreciate it! A satellite is placed in a noncircular orbit about the Earth. The farthest point of its orbit (apogee ) is 4 Earth radii from the center of...
  3. George Jones

    Exploring Black Hole Orbits: An Interactive Animation

    I'm new to PF, but in the shotr time ( a little more than 24 hours) since I registered, I've enjoyed myself. Some people hear might (or might not) be interested in the following. In order to teach myself some Java, I have developed an interactive animation that shows orbits (timelike...
  4. E

    Chemistry Orbits Representations Needed

    I've lost my Chemistry text :eek: and was wondering if anyone knew of any links that showed representations of what orbits may look like? In our halls I've seen wood models of 1p, 2p... but the text had MANY more and I can't remember the name even.
  5. C

    What is the fundamental reason for the elliptical shape of orbits?

    Why are orbits elliptical? Any ideas?
  6. S

    Question regarding Atomic Structure (orbits)

    I have my doubt,solution and question in the attachment that followed.Thanks for anybody that spend some time on this question.
  7. wolram

    Probabilities of earth like orbits, and solar systems like ours?

    What are the probabilities of Earth like orbits, and solar systems like ours?
  8. S

    Understanding Electron Orbits: Curved Space or Other Explanation?

    Do Electron orbits follow the curved space, created by the Nucleus, or is there an other explanitory reason?
  9. G

    3 Questions - Why are some orbits

    More eccentric than others? is it because of the star they revolve around, the mass of the planet? And is there a limit to an eccentricity of a planet's orbit so it could support life, how much eccentricity is too much for the planet to be inhabitable? And is it true that it is easier to...
  10. G

    Exo-Planets: 70% Eccentric Orbits - Does It Imply Rare Solar System?

    Most (about 70%) of the exo-planets we discovered has an eccentric orbit, could it have a non-eccentric planet orbiting the same sun? Also, does finding 70% of exo-planets having eccentric orbits imply our solar system is rare?
  11. D

    Solve Circular Orbit Puzzle: Calculate Mars Mass and Ratio of Satellite Speeds

    back story . i bombed my midterm . and i get a chance to make up some marks by redoing it at home . but I'm stuck on one question . so here goes . the planet Mars has two satellites, Phobos and Deimos, that orbit Mars along almost circular paths . a) Phobos average orbital radius [R] is...
  12. S

    How would constant acceleration affect a Hohmann Transfer Orbit?

    OK, I'm doing an assignment on spaceflight and I'm looking for a more complicated answer to a Hohmann Transfer. I know the conventional one, but that assumes the spacecraft has a constant velocity through the majority of the orbit. What if it doesn't? How would one calculate the time needed...
  13. A

    Calculate Magnetic Field & Velocity of Free Electron @100 nm

    How would i start to derive the magnetic field intensity and initial velocity for a free electron to circle around a radius of 100 nm?
  14. G

    Exploring the Smallest Orbital Masses: Equal and Sun-Pluto Examples

    [SOLVED] Little orbits? What are the smallest masses that could theoretically be put in space and set up in an orbital configuration. example 1 - equal masses , example 2- sun-pluto type relationship. Thanks, Glenn
  15. S

    Spacetime wave orbits black hole

    http://spaceflightnow.com/news/n0501/10spacetime/ Very interesting article about an astronomical observation of an effect which is not predicted by theory of relativity.
  16. I

    Energy for Orbits: 500km Above Earth's Surface

    This question came up on a quiz and i got it wrong. a)how much energy does it take to send a 1000kg object from the surface of the Earth to a height of 500km above the Earth's surface? b) how much energy does it take to put the same object into ORBIT at 500km above the surface of the earth...
  17. G

    Conditions for 2 Elliptical Orbits w/ Same Peri/Aphelion

    hey all, I'm just wondering, what conditions are necessary so that we could have 2 elliptical orbits such that the perihelion distance of one is the same as the aphelion of the other?
  18. F

    Atlantis shuttle and satellite orbits

    Dear Forum friends, Here's a problem I can't solve: The space shuttle Atlantis tries to put a satellite in a circular orbit with vo velocity. But they make a mistake and the actual velocity is vo(1+e). I have to find the eccentricity of the orbit when e>0 and e<0, considering |e|<<1...
  19. S

    Physics Problem: Satellites in Circular Orbits

    A satellite orbits a planet at a distance of 3.70*10^8 m. Assume that this distance is between the centers of the planet and the satellite and that the mass of the planet is 3.93*10^24 kg. Find the period for the moon's motion around the earth. Express the answers in Earth days. I tried...
  20. J

    Satellite Orbits: Meteostat Geostationary Orbit Explained

    Hi People ,Could You Please help me with this question... There's a satellite called Meteostat which in the geostationary orbit.Could you explain me why its periodic time is not exactly equal to 24 when it is viewed by an observer positioned at a point on the equator...
  21. H

    Orbits Around Sun: Exploring the Celestial Systems of Perfect Numbers

    Concerning this issue, I would like to introduce to you the architectonic approach on the structure of the celestial systems. It shows how an architect observes the laws of the cosmos. I am revitalizing an ancient but moral concept that was proposed by Pythagoras and Plato, about two and half...
  22. Q

    GRE 75, orbits, satellites and their periods

    Here is a question that I am having a hard time understanding. 75) the period of a hypothetical Earth satellite orbiting at sea level would be 80 minutes. In terms of the Earth's radius Re, the radius of a synchronous satellite orbit ( period 24 hours) is mostly: (A) 3 Re (B) 7 Re (C) 18...
  23. J

    Calculating Geostationary Orbit for a 700kg Meterological Satellite

    Hi people, could someone please help with these: On 19th June 1981, an experimental meterological satellite of mass m=700kg, was placed in a geostationary orbit using the launch vehicle Ariane. Calculate: i. The radius of the geostationary orbit given that the period of revolution of the...
  24. J

    Solving Satellite Orbits: Geostationary Radius & Speed

    Hi People I had problems solvin this question could you please help me, The question: On 19th June 1981,an experimental meteorological satellite of mass m=700 kg,was placed in a geostationary orbit usingthe launch vehicle Ariane. Calculate: a) the radius of geostationary orbit...
  25. D

    Elliptical Orbits: How They Work & Math Behind Them

    how do elliptical orbits work? in school, we never learned how to calculate the orbits of objects, their velocities, accelerations, etc. , we always worked with perfect circular orbits. what is the mathematical framework behind elliptical orbits, then?
  26. Cyrus

    Elliptical Orbits: Simple Explination & Gaining Energy

    I was wondering if there is a simple explination to elliptical orbits. I read that if i have a satelite in circular orbit, and I then fire the engine, it will gain energy, but it will cause the new orbit to be an ellipse. How come it won't just go in a bigger circular orbit?
  27. E

    Planets Orbit Sun: Why Same Direction?

    Why do all the planets orbit in the same direction around the sun?
  28. S

    Magnetic fields and Circular Orbits Question

    Hi, does anybody know what approach to take with the following problem. An electron is accelerated from rest through a potential difference of 500V, then injected into a uniform magnetic field. Once in the magnetic field, it completes half a revolution in 2 ns. What is the radius of the...
  29. E

    Are There Non-Rotating Objects in Space?

    This question has most likely been asked already: Why do planets, stars, galaxies, and other celestial objects rotate? And why do planets/stars orbit other planets/stars. If an object is to start rotating, it must initially have some non-zero net torque. But who/what is providing this torque...
  30. A

    Are There Stars with Highly Eccentric Orbits Around the Center of Their Galaxy?

    An interesting question has arised from one of the discussions around here: are there any stars that have a highly eccentric elliptical (or even parabolic/hyperbolic) orbit around the center of their gallaxy, somewhat like comets have in our solar system? And for that matter, are there any stars...
  31. J

    Transfer orbits for dummies A hillbilly tutorial.

    HELPFUL DESCRIPTIONS. a : semimajor axis For elliptical orbits, the semimajor axis is half the length of the longest line segment that can be drawn inside the ellipse. For hyperbolic orbits, the semimajor axis is the distance from the vertex to the nearest point on either branch. e ...
  32. P

    PLEASE help Kepler's third law for electrical orbits

    PLEASE help! Kepler's third law for electrical orbits Hi there! I hope someone can help me with this problem. I've been working on this for over 5 hours and I've gotten nowhere! :eek: A positron is a particle with the same mass as an electron but with a positive charge. A positron and an...
  33. R

    Solving Elliptical Orbit Problems for Space Dynamics Exam

    Got a couple of problems when lookin over my notes for Energy and velocity in elliptical orbits when studying for the space dynamics part of my exam next wed and been hit by a few problems: (i)Wit v1 being the speed at the perihelion (position of closest approach, distance a(1-e) and v2 the...
  34. S

    Low orbits, if Earth did not have an atmosphere?

    If the Earth did not have an atmosphere could you make a golf ball orbit the Earth just 1 foot above the highest point of the crust of the Earth?
  35. Coelum

    Calculating Minimum Distance between Elliptical Orbits | Orbital Distance Forum

    Forum, I'm addressing the problem of computing the minimum possible distance between two non-interacting bodies on elliptical orbits. From a general point of view, it looks like a minimization problem of a function of two variables, e.g. in the domain [0,2*pi)*[0,2*pi). This problem can be...
  36. J

    Orbit Deformation: Mars & Jupiter

    hey, i was just wondering some stuff about the orbit of planets in our solar system. is when passing jupiter, for example, the orbit of Mars deformed, turned into an ellipse? if so, does this mean that Mars is getting closer and closer to jupiter, or is there something that will keep Mars from...
  37. T

    Magnetism, Orbits, Friction-Is there a relationship?

    I hope this is the right Thread for this discussion. I was wondering by what actions do Planetary Bodies, such as the Earth, continue in their orbits, millenia after millenia and so on, without decaying and being "sucked" into the Sun, in a rather short period of Time. Something doesn't add up...
  38. A

    Determining stable orbits for other stars

    Howdy, first post, good to be here. I'm sure it will be a learning experience. My question concerns planetary formation and planet orbits for other stars, specifically the star Vega. I'm having a "disagreement" with someone who claims that Vega's mass, diameter, and density prevents the...
  39. B

    Determining orbits from R.A., Dec, & time

    Hi all, First post so here goes: Anybody know of a reference(s) for determining the orbital equations of a celestial object from it's right acsension, declination, and time? I would like to write out some equations for a few asteroids I imaged with my telescope. Thanks.
  40. P

    Why are Planetary Orbits Elliptical and not Circular?

    Greetings, people of Earth I was just wondering why the planets and other orbiting objects have eliptical orbits instead of circular ones. HELP!
  41. zoobyshoe

    Question About Elliptical Orbits

    The orbits of celestial bodies are described as elliptical. If we look at the well known means of drawing an ellipse with two tacks and a string, you can keep moving your pencil around and around and it will draw over and over the same line. The same cannot be said of an orbit. The center of...
  42. L

    Proving Least-Energy Orbits of Spacecraft

    How would one go about proving that a least-energy orbit of a spacecraft is actually the least-energy orbit? I don't want the answer, just a push in the right direction.
  43. Math Is Hard

    Orbits: Elliptical vs. Parabolic

    My Calculus textbook (Calculus , James Stewart, 5th edition, p. 720) says this: "In the 16th century Galileo showed that the path of a projectile that is shot into the air at an angle to the ground is a parabola." My astronomy teacher says that this is not technically correct, and that the path...
  44. S

    Escape velocity and formulas for circular orbits

    In my class, we developed a list of formulas for circular orbits. One of them is E/m=1/2v2-GM/r=constant. To derive escape velocity we find for what v does E=0. But an orbit of this nature is certainly not circular! How can we apply the formula?
  45. E

    Can a Vacuum Pump Simulate Planetary Orbits?

    I was just playing with this little doo-hickey http://www.phy.ntnu.edu.tw/java/circularMotion/circular3D_e.html and was wondering; How is it that Jupiter and Neptune remain in orbit even as large as they are? Is it their mass and that the Suns gravity has THAT much of an influence on them?
  46. S

    Calculate the ratio of the radii of the orbits

    Two objects of masses m and M move in circular orbits that have the same center. The force that gives rise to this motion is a force of attraction between the two objects acting along the line joining them. Use conservation of momentum and N's 2nd Law to show that they move with the same...
  47. M

    Fact or Fiction: 2 Planets Discovered in Perpendicular Orbits?

    I've just talked with someone who informed me of a T.V. special, that dealt with the discovery of two planets, that move in perpendicular orbits - relative to the other nine planets. Is this true, or was I right in assuming that it was ridiculous?
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