> that were able to escape the influence of that star.
What's the mechanism here? Is it something with greater mass that pulled it into an escape?
>What's the mechanism here? Is it something with greater mass that pulled it into an escape?
I'm a layman. Take what I say with skepticism, but I think in this case the parent poster was referring to any mechanism that ends up with a planet getting out of the orbit of the star. One such potential mechanism is gravitational slingshotting.
Let's imagine you have a planet orbiting a star. A satellite flies in towards the planet. As the spacecraft passes by the planet, it gets some of the momentum of the planet as the planet is moving around the star. The planet loses that momentum. This increases the satellite's velocity in relation to the sun. The satellite can reach escape velocity and escape the influence of the star.
Edit: alternatively to reading my explanation, you could read Wikipedia's: https://en.wikipedia.org/wiki/Gravity_assist#Explanation
There's an amazing gif of Voyager 2's slingshots. Pay attention to the velocity as it passes planets: https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Ani...
I don't see why a similar thing couldn't happen to planets.
Play with a few orbital simulators. Many are quite simple, but others allow a great deal of flexibility. It's actually quite a tricky business to get more than a few massive bodies into stable orbits -- gravity alone leads to extremely chaotic systems.