How far can a planet or dwarf planet be from our sun and remain in solar orbit?

Question

http://www.nasa.gov/vision/universe/solarsystem/newplanet-072905-images.html

Answer 1

An object can orbit the sun as long as there isn't a stronger gravitational field present. Somewhere around two light years or so out, the gravity of Alpha Centauri will interfere, although an elongated orbit with aphelion away from the α Cen system might be possible with a larger aphelion distance.The Oort cloud extends out to two light years (~120,000 AU) or more by some estimates.

Of course, an object orbiting at that distance is easily perturbed out of its orbit, and must be moving quite slowly or it will escape the sun's gravity.

Answer 2

For perturbing masses much larger than the sun, such as the galactic core, the Hill sphere is calculated as

R = D { Msun / (3M) }^(1/3)

(This is according to Wikipedia's article. This equation assumes that M>>Msun.)

Where M is the perturbing body's mass, D is the separation between the sun and the perturbing body, and R is the orbital stability radius for solar planets. If M/Msun = 1E+8 and D=35000 lightyears, then R = 52.3 lightyears.

Obviously, then, gravitational perturbations by the galactic core will not be the deciding factor in the orbital stability radius for solar planets. That maximum radius will be determined by whichever star or nearby cluster of stars imposes the greatest restriction on it.

If the limit is imposed by the aggregate of the nearby stars, then R is probably somewhere around a lightyear, or 63000 astronomical units.

Answer 3

It depends, but about 3 times the distance of Neptune would be the "Theoretical" distance.

Answer 4

depends on the amount of gravity outside our solar system and how close it is.

Answer 5

Hmmm..........................................I guess it would be around 50000 AU if the oort cloud really exists, and the orbit would be ultra-elliptical, but if the oort cloud didn't exist, then it would be around what the first guy said.