View Full Version : Discussion: Hubble Sees One Galaxy Consuming ...

2003-Aug-08, 04:33 PM
SUMMARY: A new image taken by the Hubble Space Telescope shows a large galaxy gobbling up a smaller one; a process anticipated by astronomers, but never directly seen before. Astronomers used the Keck Telescope in Hawaii to confirm that the dwarf galaxy is being consumed by measuring the rate that stars are streaming towards the larger galaxy. The stars of the smaller galaxy will eventually form a spherical halo surrounding the flattened disk of the larger galaxy.

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2003-Aug-11, 08:48 PM
This discovery compliments an article earlier this month, speculating upon the process by which galaxies are formed and grow. It would appear that galactic mergers are at lesat part of the process by which galaxies grow and that as has been speculated before that most of the dwarf galaxy stars wind up as part of the bigger galaxy's halo. A more interesting question is what happens to the dark matter in the dwarf galaxy, but that would be a question for another instrument besides Hubble to investigate. It will be interesting to learn how many of the dwarf's stars or clusters become ejected into interstellar space as a result of the interaction, and how many get incorporated into more central regions of the consuming galaxy, as opposed to the halo. Especially interesting in that regard would be the fate of a central black hole of the dwarf, which is likely to exist in any concentration of stars as big as a dwarf galaxy. As for the question of whether all galaxies started as dwarfs and accumulated mass in this fashion to become bigger spirals, I would doubt it, unless this process is demonsttrated to be far more common than it seems.
Overall, the notion of galactic mergers is good for the universe in general, as such events tend to promote new star production by stirring up, mixing, and concentrating otherwise diffuse gas and dust pockets. If galactic mergers are common then perhaps enough mass will be concentrated eventually to promote energy production for "mass-dependent organisms" despite an expanding universe to keep us going much longer than anticipated. The alternative proposal that most dwarf galaxies are remmanants of larger galaxies broken apart by interactions with each other implies a different notion, that entropy is the dominant theme regarding galactic evolution. The fact that galaxy clusters exist suggests that the effect of gravity can overcome the expansion of empty space promoting mergers. This is a concept that can be generalized to more local (smaller) realm of spiral galaxies and the more numerous dwarfs surrounding them.