The parent posted didn’t mention relativity. Just that a planet was moving at a fraction of c, which is a specific amount (let’s say, 10,000 km/s)
Since the parent poster is talking about the sun, and how such a planet with such velocity could affect it (the sun), then it’s easy to assume that the planet is moving quickly relative to the sun itself.
So, the poster’s question is equivalent to saying “if a feather collides with my body, it may do nothing. But what if the feather is super-super-super fast?! What would it do to my body??”
Ok, let’s see:
The parent posted didn’t mention relativity. Just that a planet was moving at a fraction of c, which is a specific amount (let’s say, 10,000 km/s)
Since the parent poster is talking about the sun, and how such a planet with such velocity could affect it (the sun), then it’s easy to assume that the planet is moving quickly relative to the sun itself.
So, the poster’s question is equivalent to saying “if a feather collides with my body, it may do nothing. But what if the feather is super-super-super fast?! What would it do to my body??”