Why doesnt the sun move

by vin300
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vin300 is offline
Nov24-10, 11:49 PM
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It is often safely assumed that the sun and the orbits remain relatively stationary(let's not consider precession) and the motion of the sun around the barycenter (without which the sun would be pulled towards the planets) can be neglected, but the resultant force of gravity on the sun is always changing, and yet the sun hasn't moved over these millions of years. Why?
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Panwasbipolar is offline
Nov25-10, 12:12 AM
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Doesn't the north star make it bounce a little?
Vanadium 50
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Nov25-10, 01:26 AM
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The sun does move. But in a sun-centered coordinate system it is, by definition, stationary.

davenn is offline
Nov25-10, 01:44 AM
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Why doesnt the sun move

Quote Quote by Vanadium 50 View Post
The sun does move. But in a sun-centered coordinate system it is, by definition, stationary.
yes indeed the sun does move.
firstly ... the very large scale motion as part of the rotation of the galaxy

secondary ... the sun wobbles due to the orbits of the planets around it

this 2nd motion ... the wobble... is what is allowing astronomers to discover
planets orbiting other stars :)

Borek is online now
Nov25-10, 01:59 AM
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I recall an article in popular astronomy press here many years ago, that listed over a dozen independent motions that Sun does at the same time.
ScottFlorence is offline
Nov25-10, 12:26 PM
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Our whole solar system, sun included, is moving around the massive black hole in the centre of the galaxy in the outer arm of the spiral at something around 10,000mph, but the pull of the planets does little to affect the movement of the sun due to the incredible mass of the sun in comparison to the planets, like if you were to throw a pea away from you, it would be pulling on you with it's own gravity, but not enough to really make any difference to where you are. I think Stars appear to wobble as planets pass in front of them due to the light being emitted from it being bent by the gravity of the planet, not the pull of the planet moving the sun/star
turbo is offline
Nov25-10, 12:30 PM
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The Sun (and the gravitationally-bound materials like planets, asteroids, etc) "bounces" up and down through the galactic plane on a time-scale of tens of millions of years.


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