# Solar Gravity Center

by jkg0
Tags: gravity, solar
 P: 13 Think about this hypothesis: Solar activity changes the distribution of mass on the sun. This change could move the center of mass of the sun, unless the distribution were symmetric. This would move the center of mass away from the center of rotation. This would cause a fluctuation in the gravity felt at the earth as the sun rotates. Is there any good data on solar gravity?
 Sci Advisor PF Gold P: 9,478 The center of gravity of the solar system lays well inside the surface of the sun. The seasonal change in distance of the earth from the sun has a greater influence.
Mentor
P: 15,196
 Quote by Chronos The center of gravity of the solar system lays well inside the surface of the sun.
That's not true, Chronos. The center of mass of Jupiter and the Sun is outside the surface of the Sun. The other three gas giants sometimes pulls the center of mass even further from the Sun, sometimes very close to the center of the Sun.

Besides, I don't think that that is what jkg0 was asking about. I think he's asking whether solar weather such as coronal mass ejections have an observable effect on orbits. The answer is no. These are incredibly small compared to the mass of the Sun. A large coronal mass ejection might involve 200 billion kilograms. That sounds big, but it's only 1/1019 of the mass of the Sun. To make matters worse, these are short-lived phenomena. They certainly must perturb things, but there's no way to see those perturbations. They're too small.

 P: 13 Solar Gravity Center I'm not that interested in the magnitude. I'm more interested in the variance. Low frequency changes in amplitude would slowly shift the orbits but high frequency oscillations in the center of gravity could transfer energy out to the planets. Does anyone know of an experiment where variance in the sun's gravity has been measured in short durations? If the center of the sun rotates at 14.7° per day then I would be looking for data on intervals of approximately 24.5 days.
 Mentor P: 15,196 You have to care about the magnitude. You should also care about spherical harmonics. These tiny, tiny variations will become even tinier at distance because they dissipate as a 1/r3 force, or even faster. You also need to care about the rules of this site. This forum is not a place for personal theories. Thread closed.

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