A Grand Design Challenge

While I’m incarcerated at home I thought I might as well make myself useful by passing on an interesting news item I found on the BBC website. This relates to a paper in the latest edition of Nature that reports the discovery of what appears to be a classic “Grand Design” spiral galaxy at a redshift of 2.18. According to the standard big bang cosmology this means that the light we are seeing set out from this object over 10 billion years ago, so the object formed about 3 billion years after the big bang.

I found this image of the object – known to its friends as BX442 – and was blown away by it..

..until I saw the dreaded words “artist’s rendering”. The actual image is somewhat less impressive.

But what’s really interesting about the study reported in Nature are the questions it asks about how this object first into our understanding of spiral galaxy formation. According to the prevailing paradigm, galaxies form hierarchically by progressively merging smaller clumps into bigger ones. The general expectation is that at high redshift – corresponding to earlier stages of the formation process – galaxies are rather clumpy and disturbed; the spiral structure we see in nearby galaxies is rather flimsy and easily disturbed, so it’s quite surprising to see this one. Does BX442 live in an especially quiet environment? Have we seen few high-redshift spirals because they are rare, or because they are hard to find? Answers to these and other questions will only be found by doing systematic surveys to establish the frequency and distribution of objects like this, as well as the details of their internal kinematics.

Quite Interesting.


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