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[sean2323]

hi... i was just playing with the hillspheres thing but other then making a system look awesome, what exactly do they do or show?  just wondering

[Chaotic Cow]

I think it shows the area on which the object has more pull over another object.

Like in Our Solar System.

As long as 1 object is not within the hillsphere of another planet the sun has the biggest force on it.

The more inside a hillsphere the more force the objects have on each other.

Or could be completely wrong.

[Bla]

Chaotic Cow is right.

[Chaotic Cow]

Hillspheres can grow and shrink, too.

The closer Jupiter is to our sun the smaller it's hillsphere gets because the sun gets stronger in it's pull the closer you get.

[atomic7732]

Also if earth came towards Jupiter is will shrink a bit.

[sean2323]

Thanks for the info, now i know whats going on, so for example, if an asteroid is launched toward earth through the moons hillsphere, its path would change?

[Dan Dixon]

From the Wikipedia page:

"In the Earth example, the Earth orbits the Sun at a distance of 149.6 million km. The Hill sphere for Earth thus extends out to about 1.5 million km (0.01 AU). The Moon's orbit, at a distance of 0.384 million km from Earth, is comfortably within the gravitational sphere of influence of Earth and it is therefore not at risk of being pulled into an independent orbit around the Sun. In terms of orbital period, all stable satellites of the Earth must have an orbital period shorter than 7 months."

The Hill sphere in Universe Sandbox is just showing the results of this formula:


http://en.wikipedia.org/wiki/Hill_sphere

Also if earth came towards Jupiter is will shrink a bit.

NeutronStar is right than in reality this would happen, but Hill spheres in Universe Sandbox only consider the body and its 'parent'. So in the case of Jupiter it only considers the Sun for the Hill Sphere calculation.