Distance: Pluto is 7.5 trillion meters at its furthest and 4.28 trillion meters at its closest. I will use 5.89 trillion meters as a mean.
Timeframe: Since there is literally no panel even depicting him throwing it, he did it so fast that it was obviously portrayed as being basically instantly. So I'll use 1 second as a timeframe.
Conclusion: 5890000000000 / 1 = 5890000000000 meters per second, obviously. This is around 19699 c and Massively FTL+.