I am trying to find a list of all the Mean Anomalies of the planets in the Solar System at the Epoch Jan 2000. I tried to Google it up but couldn't find any result. Can you please share the values or any link to a website that has these?

I am referring to this website for the orbital elements including the Mean Anomalies but it doesn't show the mean anomaly of Earth. On that same webpage I found the formula for Mean Anomaly as

(in degrees)Daily Orbital Motion*(t-T)

where t is the epoch and T is the Time since Perihelion. Through this website, I found the values for the variables in that equation and tried finding the Mean Anomaly for a few planets. But it doesn't seem to match with the values given on the previous website (this one).

So my main question is: Can you please share a table or website with all the orbital elements including the Mean Anomalies of the planets?

A secondary question is: Was I making any mistake while calculating the Mean Anomalies using the formula? If so please share those.


2 Answers 2


The mean anomaly isn't an orbital element. It's a time-varying thing. An orbital element is a constant, or approximately constant. On the stjarnhimlen.se site, note the large coefficient of $d$ (which seems to be time in days) for $M$, versus the small or zero coefficients of the other quantities, which really are orbital elements. The coefficient of $d$ for the earth would be 360 divided by one year. The earth's time of perihelion is around the first week of January.

I think the standard way of expressing the phase of a planet's orbit is not by giving the time of perihelion but by giving the true anomaly at a certain epoch, such as 0:00 UTC on Jan. 1, 2000. This is probably why you're not having luck googling for the time of perihelion of the earth.

Here are some orbital elements including phases from some software I wrote a long time ago: https://github.com/bcrowell/planetfinder/blob/master/PlanetFinder.java See the line beginning earth = new Planet(... and the definitions of the parameters in Planet.java. However, I can't vouch for how carefully I curated these orbital elements, so you should probably verify these elsewhere. There are lots of open-source planetarium applications out there these days, so I would just look for one that's recent and well-maintained, and dig the data out of their source code.


Mean anomaly is the fraction of an elliptical orbit's period that has elapsed since the orbiting body passed periapsis, expressed as an angle which can be used in calculating the position of that body in the classical two-body problem. https://en.wikipedia.org/wiki/Mean_anomaly

For sure, it is right, that a calculation should be made for a certain epoch.

You may ruse online service for using/editing/creating calculator. Comprehensive and useful.


  • $\begingroup$ The question is asking for numerical data. $\endgroup$
    – user15381
    Aug 6, 2021 at 14:21
  • $\begingroup$ The way to get the numerical data is to use proposed ways of calculation, or find another. That is why the question about which tools are preferable to be used above. Java, mathworks..? fxsolver.com/solve? The question about terminology and formula is resolved above. $\endgroup$
    – Lariliss
    Aug 9, 2021 at 9:05

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