Galactic escape velocity calculated as 0.2% the speed of light

New Scientist : To escape from Earth’s gravity, an object needs to be traveling at 11.2 km/s. Tilmann Piffl of the Leibniz Institute for Astrophysics in Potsdam, Germany, and his colleagues have determined that an object would need to travel 537 km/s to escape from the Milky Way galaxy. They used data collected by the Radial Velocity Experiment survey, which measured the distance from Earth to other stars and those stars’ speed toward or away from us. From the roughly 426 000 stars in the survey, they selected 90 high-velocity stars with the most precisely known speeds and positions. Then they compared models of Milky Way–sized galaxies to see which best fit the data and found that the best models had galactic masses of approximately 1.6 trillion suns. That allowed them to calculate the speed for objects in the neighborhood of our solar system. Reaching the edge of the Milky Way at galactic escape velocity is well beyond current spacecraft propulsion technologies. Chemical reaction engines require too much fuel, and highly efficient ion propulsion engines currently max out at 15 km/s.