HOW TO BUILD A GALAXY

The making of these billion-star structures has been puzzling astronomers for decades. All About Space puts together the pieces for building a galaxy

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The universe is packed with galaxies. Everywhere we look we see galaxies crammed into the cosmos, grouped in clusters and great sheets that are littered throughout space-time. The most distant galaxies ever seen have been identified by the Hubble Space Telescope as being 13.4 billion light years away. Yet these are not even the most distant galactic structures out there. It’s the first galaxies that hold the record for being the furthest away from us. However, we’re yet to see them. To do so we will need the infrared prowess of the recently launched James Webb Space Telescope (JWST), which will be able to see galaxies as they formed just 300 or 400 million years after the Big Bang – the event that threw the cosmos into existence.

Understanding how galaxies form is a bit like trying to put a jigsaw puzzle together. Think of each galaxy as being a piece of that puzzle. Because galaxies are so old and evolve so slowly, when we see a galaxy in the night sky we are just seeing a single snapshot of its long life. However, the galaxies are all at different stages of their evolution, so if we can put all these snapshots together – just like arranging the pieces of a puzzle – we can build an overall picture of how galaxies like our own Milky Way grew into the star, dust, gas and dark matter-packed structures we see today.