system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it that there is no planet that orbits the sun in the opposite direction to the other planets?
gpt
All the planets in our solar system would have emerged from what's called a 'proto-planetary disk'. This was a fairly flat disk of gas (largely H and He) and dust (solid stuff, including rock-making stuff and, at farther distances, solid ices). The planets inherited how they orbit from the direction in which the disk rotated, which would have been about the same as the spin direction of the sun.

There are several observed cases where the one planet in the system rotates in almost the opposite sense to the sense in which the star is rotating (or at least in which the sense of the orbit and the sense of the star's spin are at some large angle relative to each other). In these cases the system went through some sort of violent upheaval or maybe the star somehow had a different spin than the proto-planetary disk. This topic is a hot area of ongoing research.