Understanding Hyperbolic Orbits: The Relationship Between Foci and Trajectory

In summary, the conversation discussed the placement of an orbited body and the orbiting trajectory in a figure. It was determined that if the Earth is placed on the left focus, a comet with a hyperbolic trajectory will travel a path defined by the equation ##r - P = -2a##. It was also discussed that for a gravitational source at the left focus, r-P=-2a and for a gravitational source at the right focus, r-P=2a. The conversation also clarified that the definition of r and P can affect the resulting equation for a hyperbolic orbit.
  • #1
WWCY
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12

Homework Statement


Screen Shot 2017-11-26 at 3.46.21 AM.png


I'm rather confused as to where the orbited body is placed, and where the orbiting trajectory lies in this figure.

Is it right for me to say that if I placed say, the Earth on the left hand focus, a comet with a hyperbolic trajectory will travel a path defined by the equation ##r - P = -2a##?

Thanks in advance.

Homework Equations

The Attempt at a Solution

 

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  • #2
WWCY said:

Homework Statement


View attachment 215615

I'm rather confused as to where the orbited body is placed, and where the orbiting trajectory lies in this figure.

Is it right for me to say that if I placed say, the Earth on the left hand focus, a comet with a hyperbolic trajectory will travel a path defined by the equation ##r - P = -2a##?

Thanks in advance.

Homework Equations

The Attempt at a Solution

Looks right.
 
  • #3
haruspex said:
Looks right.

Hi, thanks for clearing that up!

Edit: Is r-P = 2a also a valid hyperbolic orbit?
 
  • #4
WWCY said:
Hi, thanks for clearing that up!

Edit: Is r-P = 2a also a valid hyperbolic orbit?
Not if the sun is at the negative focus.
 
  • #5
haruspex said:
Not if the sun is at the negative focus.

But if I do want to use r - P = 2a, and place my planet on the right hand focus, wouldn't I need to redefine r to originate from the right focus and P from the left? This gives r - P = -2a again.

Thank you
 
  • #6
WWCY said:
But if I do want to use r - P = 2a, and place my planet on the right hand focus, wouldn't I need to redefine r to originate from the right focus and P from the left? This gives r - P = -2a again.

Thank you
It depends how you are defining r and P.
If you define r as distance from the left focus and P that from the right focus then for the gravitational source at the left focus it is r-P=-2a; for the gravitational source at the right focus it's r-P=2a.
But if you define r as distance from gravitational source and P as distance from the other focus then it is r-P=-2a whichever side the source is.
 
  • #7
haruspex said:
It depends how you are defining r and P.
If you define r as distance from the left focus and P that from the right focus then for the gravitational source at the left focus it is r-P=-2a; for the gravitational source at the right focus it's r-P=2a.
But if you define r as distance from gravitational source and P as distance from the other focus then it is r-P=-2a whichever side the source is.

Thanks!
 

1. What is a hyperbolic orbit?

A hyperbolic orbit is a type of orbit in which an object travels around a central body, such as a planet or star, in a path that is shaped like a hyperbola. Unlike elliptical orbits, which are closed and repeatable, hyperbolic orbits are open and do not return to their starting point.

2. How is the focus of a hyperbolic orbit determined?

The focus of a hyperbolic orbit is determined by the distance between the center of mass of the two bodies in the orbit. The focus is located at the point where the two bodies would be if they were both stationary and the orbiting object was moving in a straight line.

3. What is the significance of the foci in a hyperbolic orbit?

The foci of a hyperbolic orbit are important because they help determine the shape and orientation of the orbit. In a hyperbolic orbit, the foci are located on the line of symmetry of the hyperbola, and the distance between the foci is equal to the length of the semi-major axis of the orbit.

4. How are hyperbolic orbits different from parabolic orbits?

Hyperbolic orbits and parabolic orbits are both open orbits, but they differ in their eccentricities. A hyperbolic orbit has an eccentricity greater than 1, while a parabolic orbit has an eccentricity equal to 1. Additionally, a hyperbolic orbit has two foci, while a parabolic orbit has only one.

5. What are some real-world examples of hyperbolic orbits?

Hyperbolic orbits are commonly observed in space missions, such as probes and satellites, that use the gravity of a planet or other large body to change their trajectory. For example, the Voyager 2 spacecraft used a hyperbolic orbit around Jupiter to propel it towards its next destination, Saturn.

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