# Is the sun anchored?

1. Feb 23, 2009

### Oscar Wilde

By "Is the sun anchored" I am referring to its place relative to the planets.

I am pretty sure the answer is yes, as the planets also exert a gravitational force upon the sun (Newton's third law). This would cause the sun to "move" somewhat, no matter how small the force exerted. Then again, I may be completely wrong. I think my general statement is right because I performed a few experiments online with a similar solar-system like structure.

All feedback appreciated,

Thanks!

2. Feb 23, 2009

### Nabeshin

Doesn't your logic show that the answer is no? If the planets exert a gravitational force on the sun, causing motion, then the sun wouldn't be anchored.

3. Feb 24, 2009

### Oscar Wilde

Yes im pretty sure it does move but I wanted to make sure I was not misunderstanding Newton's third law or something of that nature

4. Feb 24, 2009

### mgb_phys

Two objects orbit around their common centre of gravity - called the barycentre (or barycenter if you drive on the wrong side of the road)
The Earth-moon barycentre is a point inside the Earth - about half way to the centre.

For the sun all the planets in the solar system have their own effec ton the position and so it is complicated to work out and is constantly changing - but ALMOST all of the effect comes from Jupiter, the sun-jupiter barycentre is just outside the sun's surface so the sun isn't really at the centre of the solar system.

5. Feb 24, 2009

### Oscar Wilde

Thank you very much! I'll have to investigate barycentres more

6. Feb 24, 2009

### tony873004

7. Feb 25, 2009

### Oscar Wilde

Wow Tony, I investigated the site and found it to be very informative. I was surprised at the order of effects, thanks for sharing the url with me.

8. Feb 25, 2009

### flatmaster

The other online models you refer to in the OP most likely did fix the position of the sun at the center. This is a decent approximation and makes the math much easier. But these are just little java programs, not experiments.

9. Feb 26, 2009