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B The age of the Milky Way galaxy

  1. Dec 6, 2018 #1
    It seem incredulous to me that the Milky Way was formed just 13.775 million years after the start of the universe. If this is correct was it in the form that it is today?
  2. jcsd
  3. Dec 6, 2018 #2


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    All galaxies are thought to have formed from the primordial gas collapsing gravitationally. This process is in some sense ongoing, but it has long since consisted predominantly of smaller clumps merging into larger ones - that is to say, of smaller galaxies colliding to form larger ones.
    The exact process - meaning sizes and number of proto-galaxies - by which our galaxy has formed may never be known, because the collisions scramble information about pre-collision state. But the model in general is not that complicated.
    The video below shows a simulation of a galaxy similar to the Milky Way being formed. It starts with the primordial gas being roughly homogeneously distributed, before collapsing upon itself. Helpful annotations explain the process:
  4. Dec 6, 2018 #3

    stefan r

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    Wikipedia says 150 million years to form the first stars. Before that it was just gas.

    The disc of the milky way forms 8 to 10 billion years ago. So structurally things were very different. It is possible that the dividing lines between galaxy groups was already clear at 13 million years. You could mark off a clump of gas and say this part is heading for the local group and will merge into the milky way. Gas on the other side of the plane will drift toward Maffei group. That would not have any of the features we associate with galaxies. No stars, bars, or spirals.
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