The thought of traveling to a distant star is daunting enough, let alone the prospect of facing millions of years of flight time to reach the nearest galaxy. Remarkably, the discovery of galaxy-escaping hypervelocity stars may provide a solution.
In a recent paper, discussed here by Adam Crowl, Robin Spivey ponders "autonomous probes that spawn life upon arrival" as a way of reaching the Virgo cluster, which he wants to do for reasons Adam explained in his post. He's also counting on continuous acceleration at 1 g for these small 'seed ships,' but other than mentioning antimatter, he doesn't explore how this would be done, and we've seen the results Sagan and Iosif S. Shklovskii came up with for antimatter when they worked out the equations.
Let's assume that the 'slow boat' solution is the only practical way to proceed. Here I think Adam's suggestion that we take our environment with us rather than building a worldship is sensible, flinging a small star and planet out of the galactic core toward the destination. Ray Villard pondered the same question back in 2010 in an online piece called "The Great Escape: Intergalactic Travel is Possible." He points to the four million solar mass black hole at the center of the Milky Way as the only conceivable way to impart the needed kinetic energy to a star.
Here's how Villard describes the mechanism:
The theory is that a star could be slingshot out of a binary star system if the stellar duo swung close to the central black hole. The hole's gravitational tidal forces would break apart the pair's gravitational embrace.
The companion star orbiting in the direction of the black hole would pick up momentum and plunge toward the black hole. In accordance with Newton's third law of motion — action-reaction — the other binary companion would go whizzing off with the same velocity but opposite direction away from the black hole.
In just a few thousand years the star would ascend out of the galactic plane and hurtle deep into intergalactic space. The persistent tug of our Milky Way's dark matter halo would slow it down but the star would never fall back into the Galaxy.
Using ESO's Very Large Telescope, astronomers have recorded a massive star moving at more than 2.6 million kilometres per hour (1160 km/sec). Credit: ESO.
We do in fact know about a number of such hypervelocity stars, some of which may be moving fast enough to exceed galactic escape velocity. Consider this: Ordinary stars in the Milky Way have velocities in the range of 100 kilometers per second, while some hypervelocity stars near galactic center show velocities of ten times that, closing on 1,000 km/sec. Meanwhile, a team led by Tilmann Piffl (Leibniz Institute for Astrophysics, Potsdam) that has been working with high-velocity stars has calculated escape velocity for objects in the vicinity of our own Solar System. The team uses data from the Radial Velocity Experiment (RAVE) survey.