Do nearby stars have an effect on the Sun and its planets?

[Erus]

The Sun has effect on its Planets (and vice versa). The Planets have an effect on their Moons (and vice versa). Do nearby Stars effect the Sun (and vice versa)?

If this is true, how large of an effect could there be? What would be the cause of the effects? Would it have anything to do with how many planets, what types of planets, the Sun has? Could it be (add on) cause for life?

 

[tony873004]

If you mean affect gravitationally, the answer is yes, but it's very insignificant. Unless the star passes really close to the solar system (? < 500 AU), it won't have any significant effect on the planets' orbits such as changing their eccentricities or inclinations. It will have an effect on objects in the Oort Cloud and possibly the outer Kuiper Belt. A current theory suggests that a passing star or brown dwarf was responsible for Sedna's current orbit.

As far as life... if a star passed that close, Earth would probably be right in the middle of its Oort Cloud or Kuiper Belt, assuming it had these. That might give the opportunity for Earth to get seeded from an extra-solar comet.

 

[Phobos]

Welcome to Physics Forums, Erus & tony873004!

If this is true, how large of an effect could there be? What would be the cause of the effects? Would it have anything to do with how many planets, what types of planets, the Sun has? Could it be (add on) cause for life?

Like tony said, the direct gravitational effect is small (try the easy math for the differences in the gravitational force from the sun-earth vs. a nearby star-earth). Over billions of years, the little chaotic pertubations may add up to something interesting (now that math model would be tough!)

So I'll just add another point that the net gravitational result of the galaxy's influence on the solar system (i.e., our orbit around the galactic center) sends us up and down through the galactic plane where there may be more effects on the solar system when we pass through that denser region.