Where is the Solar system's barycenter located? The solar system as a whole, Where is the center of the mass for the combined mass of the Sun, inner planets, and gas giants, is it inside the Sun? Is there an AU measured distance of it?

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    $\begingroup$ Bingo! This diagram: cloud10.todocoleccion.online/libros-segunda-mano-astronomia/tc/… $\endgroup$ – Euro Micelli Jan 8 at 3:58
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    $\begingroup$ My answer here has two diagrams of the Solar System barycentre relative to the Sun, covering the period from 1945 to 2051. astronomy.stackexchange.com/a/28036/16685 $\endgroup$ – PM 2Ring Jan 8 at 5:06
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    $\begingroup$ Although my answer (linked in the previous comment) is to a different question, I think it covers what you're asking in this question. It doesn't give any distance measurements, but you can estimate those (in proportion to the solar radius, 695700 km) roughly by eye. $\endgroup$ – PM 2Ring Jan 8 at 5:20
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    $\begingroup$ Thanks for the response guys. Yes, those diagrams are very good. but they lost me even more, I was looking for a fixed point with AU distance that I can use for calculations. Seems like the center of mass moves very quickly. Unexpected. I was thinking that it must be a very stable point to use as a reference. $\endgroup$ – Majoris Jan 8 at 23:02
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    $\begingroup$ Voting to reopen. OP is asking for quantities, not just a picture. $\endgroup$ – Mike G Jan 9 at 21:34

The solar system barycenter (SSB) is sometimes inside the Sun and sometimes outside. As an observer outside the solar system could detect with Doppler spectroscopy, the Sun is what's wobbling around.

The Sun's offset from the SSB is a vector sum of roughly:

  • 0.00496 au ±5% away from Jupiter
  • 0.00272 au ±6% away from Saturn
  • 0.00083 au ±5% away from Uranus
  • 0.00155 au ±1% away from Neptune

The other planets contribute much smaller amounts to the total. Each planet's contribution is proportional to the product of its mass and its orbital distance.

When these components add constructively as in 2020-2023, the center of the Sun can be as far as 2 R away from the SSB. When they cancel as in 2029-2030, the center of the Sun is within 0.5 R of the SSB. The solar radius R is 0.00465 au, shown here with a dashed line.

Plot of Sun-SSB distance vs. time

  • $\begingroup$ Nice graph! Did you create it using JPL Horizons data? You can clearly see the ~20 year period of the Jupiter-Saturn conjunction cycle. It'd also be interesting to see the corresponding graph of the SSB's (heliocentric) ecliptic latitude. Of course, the 20 year period would be less obvious in the direction graph, but I assume there'd be a ~60 year period (60 ~= 5 Jupiter periods ~= 2 Saturn periods). $\endgroup$ – PM 2Ring Jan 18 at 19:17
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    $\begingroup$ @PM2Ring Almost: I used Skyfield to read JPL DE430. $\endgroup$ – Mike G Jan 18 at 19:22
  • $\begingroup$ Nice. Your comment here prompted me to learn about Horizons, and I've written some Python code that can do simple retrievals of Horizons data. I'm using it to construct a better barycentre diagram for my answer here. (It's almost ready to post, but I have another unrelated coding project I need to finish first). $\endgroup$ – PM 2Ring Jan 18 at 19:39

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