According to the paper it's moving at 1700km/s (see also: https://www.wolframalpha.com/input/?i=4+million+miles+per+hour https://www.wolframalpha.com/input/?i=4

According to the paper it's moving at 1700km/s (see also: https://www.wolframalpha.com/input/?i=4+million+miles+per+hour https://www.wolframalpha.com/input/?i=4+million+miles+per+ho... ). I prefer "20.4 light seconds per hour" :-) It's also 0.56% the speed of light. The escape velocity of the Milky Way is 500km/s.