B Enlarging Planetary Orbits: Evidence of the Solar System's Evolution?

[Sanborn Chase]

Is there any evidence of the enlargement of planetary orbits over time? Are the planets moving further from the sun?

 

[mfb]

The orbits change their semi-major axis all the time, in both directions, based on the gravitational influence of other objects. There is a long-term trend outwards as the Sun loses mass, but over timescales we can observe this is completely drowned by the short-term variations.

 

[Sanborn Chase]

Thanks for your response, mfb. It's a great help.

 

[newjerseyrunner]

There is evidence for lots of orbital shakeup in the early years of solar system: https://www.nasa.gov/topics/solarsystem/features/young-jupiter.html

 

[Janus]

To add to mfb's reply, here are two tables which give how orbital elements change with time.
The first is over the time period of 1800AD-2050AD:
https://ssd.jpl.nasa.gov/txt/p_elem_t1.txt

and the second for the time period of 3000BC-3000AD
https://ssd.jpl.nasa.gov/txt/p_elem_t2.txt

Note that in the first column (a), which gives the average orbital distance in AU and the change in AU per century, the Earth's orbit (EM bary), increases on average over the shorter time scale, but decreases on average over the longer time scale.

 

[Sanborn Chase]

Thanks, Guys.