The Horizon of Future Intergalactic Travel

I show that non-relativistic objects traveling in intergalactic space at an initial peculiar velocity v will traverse in the future of the LCDM cosmological model a maximum comoving distance of ∼(v/1.7H 0), irrespective of travel time, where H 0 is the Hubble constant. This follows from the future exponential growth of the scale factor. Hypervelocity stars escaping the halo of the Milky Way galaxy will not go beyond a few tens of comoving Mpc, even over the trillions of years that represent the lifetime of low-mass stars. To reach beyond the Virgo cluster of galaxies, requires an initial peculiar speed ≳3 × 103 km s−1, a hundred times faster than the chemical rockets launched to space so far.