“This is the most colossal cosmic smash-up ever witnessed in the universe” says New Scientist:
A bundle of galaxies, nicknamed Pandora’s cluster, turns out to be the result of a violent crash between at least four separate galaxy clusters that lasted hundreds of millions of years…
The splattered remains suggest several galaxy clusters have collided over about 350 million years. Bright visible galaxies make up 5 per cent of the mass, while searingly hot gas that glows in X-rays makes up 20 per cent. The rest is dark matter, a mysterious invisible substance that gives itself away only because its gravity bends light from background galaxies.
“See there, wouldn’t want to be there,” says David Klaus:
It’s a rough clue to what we’re going to look like when Andromeda hits the Milky Way in about three billion years. Depending on where it is in its galactic orbit the Solar System will either be eaten by the giant multiple black hole as the galactic centers merge, or flung out of the galaxy completely.
That would be bad.
[Thanks to David Klaus for the story.]
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I’ve seen this shot before. It’s used to “prove” the existence of dark matter. The gravitational center of the cluster isn’t where all the flourescing is, therefore there is a lot of mass to either side of the pretty red and blue glow which isn’t interacting in the collision. That proves dark matter. Or that its inert. Or that it pays to use the Yellow Pages… I forget which. I’m just a wee bit skeptical about the existence of 90% of the universe that happens to be invisible, and doesn’t do anything.
Taral is right to suspect we know less than the PR supposes about the missing dark matter & dark energy.
But…colliding with Andromeda will disrupt star orbits, yes–and quite seldom, their solar systems. Stellar densities even in spirals are so low there’s little chance we’ll get disrupted significantly. We’ve been cruising through the same stellar density for ~5 gigayears without much harm. Whew!
Just a thought, added in hope Beford will read it. Is there any chance that the supposed missing mass of the universe is a Relativistic effect of its expansion. Farther galaxies recede faster, are red-shifted more, and surely ought to appear more massive to us? The effect of recession is, according to Relativity, indistinguishable from rest mass. The red-shift of distant galaxies should be indistinguishable from a red-shift due to gravity.