MadSci Network: Astronomy
Query:

Re: Hiow long is the apsidal precession?

Date: Sat Jan 31 10:35:59 2015
Posted By: Phillip Henry, Staff, Physics, Lockheed Martin & Florida Tech
Area of science: Astronomy
ID: 1421498975.As
Message:

Thank you David, an excellent question! So is the apsidal precession 112ky 
or 134 ky - which answer is right? I could not determine the source for 
the Calendar Wiki data. However the short answer: neither, or perhaps 
both. Allow me to explain.

First the basics. The earth's orbit is not a perfect circle. It follows an 
elliptical path thru the heavens. The period apsidal precession is 
about 112,000 years. Calculations need to account for gravitational 
influences, which is not necessarily limited to that of the earth and sun. 
If attempting to measure, what's your reference? The solar system itself 
is following an orbit through our galaxy. According to E.M. Standish, the 
observed precession of earth's perihelion is 11.45 arc-seconds/year, which 
computes to approximately the 112 year number quoted. I hope this answers 
your question. For more reading, I would suggest:
 http://www-
spof.gsfc.nasa.gov/stargaze/Sprecess.htm
 http://www.astro.gla.ac.uk/honours/labs/solar_system/papers/laskar.pdf
 h 






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