Friday, 17 February 2006


Our Galaxy is a monster that eats it's neighbours. And a messy eater, at that. From the ABC.
Astronomers have released new evidence to show that a region of stars in our galaxy known as the Arcturus stream is the digested remains of what was once a neighbouring galaxy.

The evidence is among the first to come from the largest star study to date, with data from 25,000 stars just released at a US astrophysics workshop.

Dr Quentin Parker of Sydney's Macquarie University and the Anglo-Australian Observatory is head of data management at the international Radial Velocity Experiment (RAVE), which uses Australia's UK Schmidt telescope.

Dr Parker says the latest results provide a smoking gun for the argument that the Milky Way is a voracious cannibal that devours its neighbours.

"We've confirmed the Arcturus moving group as being a star stream, which indicates a disruptive galaxy spiralled into our own," he said.

"Ours is a large galaxy and it has been eating other galaxies; it's been hungry. We can see what it's eaten by the crumbs that are left over from its meal."

It is another bit of evidence for the now widely accepted cannibal, or accretion, theory of galactic evolution, Dr Parker says.

This theory says the gravitational pull of large galaxies sucks in smaller ones, making large galaxies like our own a sort of cosmic melting pot.

Dr Parker says the RAVE measurements show stars in the Arcturus group are travelling at a similar velocity and in a similar direction through space, indicating they were once part of a coherent system.

One fact not stated : how long ago this dining experience happened. Or when the next one might occur. You see, when you live in an Unfashionable Outer edge of a Spiral Arm, as we do, when Galaxies collide and start merging, things like nebulae and dust clouds can make the local neighbourhood a very lively place. Or rather, deadly.

Without knowing more of the detail, I can't speculate what the likely consequences of such an event are. Galaxies are, for the most part, lots of vacuum after all, and it's possible that the gravitational effects might be un-noticeable except over eons rather than geological ages. But sharing one's personal space with an intruding nebula might be haqzardous to one'e health, and should the one in a bazillion happen and you get a collision anywhere within a few hundred light years, it could be messy.

Call it indigestion.

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