How many extrasolar planets do we know about? © Getty Images

How far would we need to travel to leave our Galaxy?

It depends on whereabouts you want to get to; our vast Galaxy is thousands of light-years across, but for a decent vantage point you would need to travel much further.

Asked by: David Pollock, Cumbernauld

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Our Galaxy, the Milky Way, is a disk of stars about 100,000 light-years across, and about 1,000 light-years thick. The Sun is situated about halfway from the centre and is near the middle of the disk in the vertical direction.

So, to leave our Galaxy, we would have to travel about 500 light-years vertically, or about 25,000 light-years away from the galactic centre. We’d need to go much further to escape the ‘halo’ of diffuse gas, old stars and globular clusters that surrounds the Milky Way’s stellar disk.

Finally, if we wanted to go far enough to see our entire Galaxy in all its glory, we’d need to travel about 48,000 light-years vertically. It’ll be a long time before we have the technology to do this, or even to send a telescope there, so for now we’ll just have to enjoy the incredible images we have of other spiral galaxies.

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