Perihelion Pass Dates for Planets - Alex's JS Orrery

  • Context: Undergrad 
  • Thread starter Thread starter twinsen
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Discussion Overview

The discussion revolves around the development of a JavaScript orrery to display planetary positions and the need for perihelion dates to calculate the Mean anomaly and Eccentric anomaly using Kepler's equation. The scope includes technical aspects of orbital mechanics and programming.

Discussion Character

  • Technical explanation
  • Exploratory

Main Points Raised

  • Alex seeks information on previous perihelion dates for planets to aid in his JavaScript orrery project.
  • One participant suggests an obsolete shareware that provides perihelion data.
  • Another participant points to the HORIZONS system at JPL as a definitive source for ephemeris data.
  • A later reply comments on the HORIZONS system's reference to '9 planets', which some participants find contentious.
  • Alex acknowledges the suggestions and expresses a need for further reading on the parameters involved in orbital mechanics.

Areas of Agreement / Disagreement

Participants generally agree on the utility of the HORIZONS system for obtaining perihelion data, but there is a disagreement regarding the classification of celestial bodies, as indicated by the comment on the number of planets.

Contextual Notes

Alex mentions that he has not covered the relevant parameters in his course yet, indicating a potential gap in knowledge that may affect his understanding of the topic.

twinsen
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Hey

I am writing a basic javascript orrery which will display the position of the planets orbiting the sun. Using keplers equation I am going to find the true anomaly and the radius at the current time and then plot the points to a 2d grid.

The problem is I need to know the time that has elapsed since perihelion so I can calculate the Mean anomaly. I plan to use the iterative Newton method to get the Eccentric Anaomaly and from that work out the true anomaly.

Do you guys know where I can find a list of previous perihelion dates where the planets were at their closest approach?


Thanks
Alex
 
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D H said:
The definitive source of ephemeris data is the HORIZONS system at JPL. Website: http://ssd.jpl.nasa.gov/?horizons.

It's nice that that site still lists that we have '9 planets'.
 
rewebster said:
It's nice that that site still lists that we have '9 planets'.

BAH! Semantics !:rolleyes:
 
Thanks guys

Ill check out the site tommorow looks like ill have to do a bit more in depth reading onto all the different parrameters I've not really covered this stuff in my course yet but so far I see its just basic trig geometry.

Cheers

Alex
 

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