#21 The Milky Way--One Less Thing To Worry About

Good News for a change. Concerns over those pesky dwarf-galaxies threatening our own have been allayed. Oh, one of them in our "local group" will collide with us all right, and fairly soon, but the damage would be, in all probability, minimal. In a new study released Monday, coordinated by Ohio State, a group of astronomers from California to the UK have determined through computer modeling that the halo of DARK MATTER around the Milky Way will be what saves us from annihilation. Whew! Close call.

It's only been within my lifetime that other galaxies were definitively proven to be other galaxies. Before that they were "nebulae" or cosmic clouds circling what was considered the center of the universe: the Milky Way itself. I can well remember my old science textbooks referring to the Crab and Andromeda nebulae, and the Magellanic Cloud. Nothing about galaxies. There were early speculations, especially after Galileo spotted stars amidst these formations. None other than the polymathic Immanuel Kant, for example, thought they might conceal "island universes." But it ultimately took two "Hubbles" to pin it down. First, Edwin Hubble himself got hold of a powerful enough telescope in the 1930's to confirm that these island universes were not part of our galaxy, and even started classifying them (ours is a Spiral, which we see only from within snd sideways in the night sky). And later, his namesake Hubble Space Telescope finally left no doubt. High-school textbooks have I hope caught up by now.

Anyway, lead-astronomer Stelios ("star"?!) Kazantzidis and his colleagues performed detailed computer simulations to determine what would happen when a satellite galaxy collides with a spiral galaxy buffered by Dark Matter, like ours. Result: lovely "puffy edges," as he calls them. The studies show that the satellite galaxy would gradually disintegrate, while its gravity tugged on the edges of a larger galaxy, one like the test-model Andromeda, drawing out stars and other materials in the process. Kazantzidas concludes:

We can't know for sure what's going to happen to the Milky Way, but we can say that our findings apply to a broad class of galaxies similar to our own. Our simulations showed that the satellite galaxy impacts don't destroy spiral galaxies--they actually drive their evolution, by producing this flared shape and creating stellar rings--spectacular rings of stars that we've seen in many spiral galaxies in the universe.

Who would have thought that Dark Matter could be such a great friend. And a wonderful decorator to boot. Put's my mind at rest. I feared for the worst, but now I'm rather looking forward to that collision. Our Milky Way is already a handsome piece of work, but a few puffy edges would be a fabulous final touch. Cosmological feng shui. Just think of that when the weight of the world's problems are getting you down.
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