Cosmic Swirly Straws Feed Galaxy

I came across this video on youtube and was intrigued because the title seemed like a crossword clue (to which I couldn’t figure out the answer). It turns out that it goes with a piece in the Guardian which describes a computer simulation showing the formation of a galaxy during the first 2bn years of the Universe’s evolution. Those of us interested in cosmic structures on a larger scale than galaxies usually show such simulations in co-moving coordinates (i.e. in a box that expands at the same rate as the Universe), but this one is in physical coordinates showing the actual size of the objects therein; the galaxy is seen first to condense out of the expanding distribution of matter, but then grows by accreting matter in a complicated and rather beautiful way.

This calculation includes gravitational and hydrodynamical effects, allowing it to trace the separate behaviour of dark matter and gas (predominantly hydrogen).  You can see that this particular object forms very early on; the current age of the Universe is estimated to be about 13 – 14 billion years. When we look far into space using very big telescopes we see objects from which light has taken billion of years to reach us. We can therefore actually see galaxies as they were forming and can therefore test observationally whether they form as theory (and simulation) suggest.

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