Trajectories of planets using reduced mass and CM frame

In summary, the reduced mass of a system is used to analyze the motion of a planet in the non-inertial frame of a star. This results in a conic trajectory, but this is only the trajectory as seen from the star. In the CM frame, the trajectories are still conics with the focus at the CM. The star also follows a conic trajectory with the focus at the CM of the system. The trajectory of the planet seen in the CM frame may differ from the one calculated using the reduced mass in the star's frame. This can be seen in detailed plots of the orbits when the observer moves from the CM frame to one of the bodies.
  • #1
Soren4
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In planetary motion, the reduced mass of a system [itex]\mu[/itex] is used in order to study the motion of the planet [itex]m[/itex] in the non-inertial frame of the star [itex]M[/itex]. Using [itex]\mu[/itex] the trajectory of [itex]m[/itex] turns out to be a conic. But this is the trajectory of the planet [itex]m[/itex] as seen from the star [itex]M[/itex], correct?

I read that in the CM frame the trajectories are still conics (ellipses for istance) but that the focus is in the CM. Moreover the Sun (or the star) also follows a conic trajectory with focus in the CM of the system.

Is the trajectory of the planet seen in CM frame different from the one calculated using [itex]\mu[/itex] (and so the one in the [itex]M[/itex] frame)?
 
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  • #2
Soren4 said:
In planetary motion, the reduced mass of a system μμ\mu is used in order to study the motion of the planet mmm in the non-inertial frame of the star MMM. Using μμ\mu the trajectory of mmm turns out to be a conic. But this is the trajectory of the planet mmm as seen from the star MMM, correct?

I read that in the CM frame the trajectories are still conics (ellipses for istance) but that the focus is in the CM. Moreover the Sun (or the star) also follows a conic trajectory with focus in the CM of the system.

Is the trajectory of the planet seen in CM frame different from the one calculated using μμ\mu (and so the one in the MMM frame)?

if you see the resources on the net detail plots are there of the orbits when the observer moves from centre of mass frame to one of the bodies.

for example
[PDF]The Two-Body Problem - KSU Math Home
https://www.math.ksu.edu/~dbski/writings/twobody.pdf
 

Related to Trajectories of planets using reduced mass and CM frame

1. What is the reduced mass of a planet and how is it used in calculating trajectories?

The reduced mass of a planet is a mathematical concept used in the two-body problem, which describes the motion of two objects orbiting each other under the influence of their mutual gravitational attraction. It is calculated by taking the product of the masses of the two objects and dividing it by their sum. This value is used in calculating the trajectories of planets because it simplifies the equations and allows for a more accurate prediction of their motion.

2. What is the CM frame and how does it relate to the motion of planets?

The CM (center of mass) frame is a reference frame in which the total momentum of a system is zero. In the context of planetary motion, it is used to describe the motion of a planet and its central star as a two-body system, with the center of mass located at their common point of gravity. This frame allows for easier calculations and analysis of the motion of planets.

3. How does the reduced mass and CM frame affect the stability of planetary orbits?

The reduced mass and CM frame have a significant impact on the stability of planetary orbits. In a two-body system, the reduced mass determines the strength of the gravitational force between the two objects, while the CM frame allows for a simplified analysis of the motion. These factors play a crucial role in determining the stability and longevity of a planetary orbit.

4. Are there any limitations to using reduced mass and the CM frame in predicting planetary trajectories?

While using reduced mass and the CM frame is a useful approach in predicting planetary trajectories, there are some limitations to its accuracy. These methods assume that the objects are point masses and do not take into account the effects of other celestial bodies or external forces on the system. In reality, these factors can have a significant impact on the motion of planets and may need to be considered for more precise predictions.

5. How do scientists use the concept of reduced mass and the CM frame to study exoplanets?

Scientists use the concept of reduced mass and the CM frame to study exoplanets by applying the same principles used to study planets in our solar system. By analyzing the motion of exoplanets, scientists can determine their mass, orbit, and other key characteristics. These calculations can provide valuable insights into the formation and evolution of exoplanet systems and help us better understand our place in the universe.

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