Interstellar travel at speeds slower than light isn't really viable in human lifetimes from Earth, but it would be in many cases in the center of the Milky Way galaxy where the distances between stars are ten to a hundred times smaller, on average. So, a trip to the next solar system could take as little as four years at 1% of the speed of light, which is fast, but not technologically unattainable.
If we lived in the center of the Milky Way, we would look up at a sky thick with stars, up to 1 million times denser than we’re used to seeing. The closest star to our Sun is about four light-years away. In the center of the galaxy, stars are only 0.4 to 0.04 light-years apart. In the inner 10,000 light-year region of the Milky Way, the galaxy’s spiral arm structure transitions into a dense, spherical “bulge” of stars. At its heart — and the dominant force in that area of the galaxy — is a supermassive black hole approximately 4 million times the mass of the Sun, called Sagittarius A* (pronounced Sagittarius A star).
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[T]he average distance between any two stars in our galaxy. . . . [is] about 5 light years, which is very close to the 4 light year distance between our Sun and Alpha Centauri.
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In the central part of some galaxies, interstellar distances average as little as 0.008 light years to 0.013 light years. So, one could travel from one star to the next there in 8-13 years at only 0.1% of the speed of light (about 300 km/s). And, even in very dense galaxies it is rare for stars to collide:
Even at these high star densities, collisions are rare. Globular clusters have stars in their centers called “blue stragglers,” which astronomers think are new, massive stars formed by the collision of two old, lower-mass stars. Fewer than one in every 10,000 globular-cluster stars are blue stragglers, which suggests how rare stellar collisions are even in these extreme environments.
These collisions would take place only over billions of years.
6 comments:
On a round trip to Mars the radiation dose from cosmic rays can be equal to a lifetime dose. There is also the question of the damage to electronics such as computers. Already highly parallel machines on Earth have to have procedures to deal with cosmic hits. What are the implications for long term interstellar missions away from the protective magnetic field of a star? Is the cosmic ray flux higher in the galaxy center?
I suspect that coming up with some sort of shielding wouldn't be insurmountable, although it isn't a technological front that I'm intimately familiar with.
I imagine these star systems might be a good place for an interstellar civilization to expand but probably not develop. With stellar distances that close, they're probably getting pasted with comet hits constantly.
@Ryan Actually, the probability of collisions is much lower than you'd intuitively think. Space is really, really empty.
Not that empty of comets. You don't need to be THAT close to perturb a lot of their orbits simultaneously. I'm not saying this collisions would happen on the scale of a human life, but if they are a couple of orders of magnitude more frequent than here (which seems pretty likely given how close these stars are) that could pose a real challenge for complex life.
It is not at all clear that shielding will work. NASA was looking into that for Mars and I do not know how that has turned out. When a cosmic ray hits, a shower of particles is produced just as in the case of a cosmic ray coming down through the atmosphere.
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