You can't fool me with that label of "diameter", I know that's actually a trench with an exhaust port that if successfully fired into will cause a cascading failure
Okay so I forgot how big the sun is and had that absentminded mental picture moment of "oh it would make a big bang as something 3/4s the size of the sun would hit it"...
This picture was a very helpful reminder of just how out to lunch that thought was. Don't trust your absent thoughts, folks 😅
The more I learn about the sun, the more I realize those ancient civilizations who worshipped it got it right. Look at that thing it’s fucking huge, scary, and it’s like right there.
Now I'm imagining the type of event that could cause a planet to move at such a significant percent of c that you could disrupt the sun with it. I don't think we're gonna get a planet moving that fast. I think we'd be limited to stellar core remnants to get that kick in velocity.
As it is, our entire solar system is orbiting at 514,000mph or about 1/1300th the speed of light relative to the center of the galaxy. And the Milky Way Galaxy is moving at about 1.3 million mph through the universe.
We are going to collide with the Andromeda galaxy maybe 1 billion years before the sun fizzles out. Something there with opposite galactic orbit from us could smack into our sun at over 700 km/s.
That's not how relativity works. Moving quickly relative to what? The planet might be moving slow relative to the local objects where it began its movement, but the local objects at it's origination point were also moving at some speed, and the group of objects that the local group was in were also moving at some speed, etc etc. And likewise our sun isn't stationary, it's also moving relative to everything else, so you could just as easily say the planet is stationary but our sun was moving very quickly toward the stationary planet. There is no thing as an absolute slow/fast when you're talking about bodies in space. There are tons of ways that a planet sized object could have a fraction-of-c speed relative to our sun.
And there are "rogue planets" out there. They aren't held into any orbital system, they're just flying free in empty space. So that part is true as well. It would be very unlikely that some of them AREN'T moving extremely quickly relative to the sun.
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??"