Galactic surprise: New find overturns theories how our galaxy evolved
Our galaxy wasn't always the beautiful cosmic ballet it is today. Billions of years ago, the Milky Way was a chaotic jumble of stars and gas moving every which way.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Jan 7, 2013
Studies of stars in our galaxy also came to that result a while back.
Bulge, Halo & Globular clusters were ~13 to ~10 billion years old.
The thick disc is ~10 to ~8 billion years old.
The medium disc (about 3000 light years thick) is ~8 to ~5 billion years old.
The thin disc with the spiral arms is 5 billion years old to the present day.
The barred spiral configuration appears to date back to the time of the thick disc, and may even be the age of the halo. Also of note is that several very metal poor stars are orbiting in the disc @ typical disc velocity and may be a relic of the original barred spiral configuration which evolved its current ring barred shape with time.
Most likely our galaxy began as an S shaped barred spiral (or prolate E) and its evolution to a ringed barred spiral came as a result of the accumulation of gas and stars through collision and mopping up of dwarf galaxies and bits of gas with time.
The Sgr dwarf collision appears to have had a lot to do with the current shape as a ringed barred spiral, interactions with big companion galaxies appear to be responsible for telescoping the bar, the magellanic clouds appear to be recent very big additions to the retinue of the milky way, and are likely to merge resulting in the formation of a classical spiral. Their tidal effects have warped the disc into waves at least as high amplitude as the intermediate disc.
Have a nice day: Ag
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