Getting out of the galaxy might take an antimatter engine. Future explorers departing the Milky Way will have to boost their spaceship to 0.2 per cent of the speed of light, according to a study of fast-moving stars in our galaxy.
Tilmann Piffl at the Leibniz Institute for Astrophysics in Potsdam, Germany, and his colleagues used the latest data from the Radial Velocity Experiment (RAVE) survey. The survey uses the Anglo-Australian Observatory's 1.2-metre Schmidt telescope in Siding Spring, New South Wales, Australia, to measure the distances to stars and the speeds at which they are moving away or towards us, among other properties. The latest survey studied about 426,000 stars.
From this survey and a previously published star catalogue, the team selected 90 high-velocity stars whose speeds and positions had been determined most precisely. Some of them are moving at speeds of more than 300 kilometres per second, about one-thousandth of the speed of light.
The team then studied various models of Milky Way-sized spiral galaxies to determine which one best fit the observed stars and their velocities. The most suitable simulated galaxies had masses of about 1.6 trillion suns.
"People used to say it was twice that," says team member and astronomer Joss Bland-Hawthorn at the University of Sydney in Australia. "It's not as massive as we thought
Engine trouble
With the likely mass of the galaxy in hand, the team calculated the escape velocity for objects in the vicinity of our solar system. To escape the gravitational clutches of our galaxy, a spaceship would need to zoom out of our solar system and hit 537 kilometres per second. For context, a rocket needs to roar off at just 11.2 kilometres per second to escape Earth's gravity.
Conventional rocket engines would never make it. The chemical rockets that power most spacecraft today would require too much fuel, and even high-tech ion engines – which are efficient enough for long journeys around the solar system – max out at about 15 kilometres per second.
But Bland-Hawthorn speculates that a propulsion system powered by the energy released by combining matter with antimatter could do the trick. The challenge, of course, would be find ways to create and confine large amounts of antimatter. "I know it's a crazy idea, but if you had lots of matter and lots of antimatter, you could power a spaceship out of the galaxy," he says.
Journal reference: arxiv.org/abs/1309.4293v1
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