Through the 'magic' of gravity. The gravitational field of the Sun reaches out past our solar system and eventually merges with the fields produced by other stars in the Milky Way. The Sun's sphere of influence is literally light years across, and any object within this sphere can be affected even though they may be a million years in travel time, and trillions of miles away from the Sun. On such a scale, Hale-Bopp, with a period of 'only' 2800 years, is pretty close by. Pluto's period is about 264 years, so Hale-Bopp's orbit is only about 5 times larger based on Kepler's Third Law ( P^2 / D^3 = constant)