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  • Most things in the universe happen too slowly for us to see them happening. Stars like the

  • sun take tens of millions of years to form, and hundreds of millions of years to orbit

  • their galaxies; colliding galaxies take billions of years to merge. And yet we have a pretty

  • decent understanding of how all these things happen, because there are so many of them

  • in the observable universe that we can look out and see different versions of similar

  • events happening in different places, and because light takes time to get here we see

  • places at different distances at different times thoughout the history of the universe,

  • and from all that we can piece together an understanding of how stars are born and how

  • they die, how galaxies develop and interact, and so on. It's kind of like if you only

  • had ten minutes to study how humans growyou couldn't see any one person grow very much

  • in that time, but by looking at humans of different ages all around the world, you can

  • get a pretty good picture of what a human life looks like.

  • However, the very first galaxies to ever form were so small and dim that we don't have nearly

  • as good an idea of how baby galaxies are born as we do about how they behave and interact

  • later in life.

  • Our current understanding is that in the early universe, before any stars had formed, everything

  • was just spread-out gas and a lot of dark matter. Gravity would have caused slightly

  • denser areas of dark matter to attract into clumps, pulling in bits of gas until they

  • were dense enough on their own to gravitationally collapse and start thermonuclear fusion. A

  • star. Many stars. Clusters of stars and their associated dark matter attracted together

  • and merged, and then those clustered-clusters clustered together, eventually forming the

  • most distant (and longest-ago) galaxies we see today.

  • But we don't know exactly how soon after the big bang the clumps of dark matter and

  • gas formed; or when during the process of clumping and clustering the first stars ignited;

  • or if there was a minimum dark-matter-clump size necessary to attract enough gas to form

  • stars; or if the very first star clusters came together to form galaxies at allthey

  • might have been so small and fragile they were blown apart when their own stars went

  • supernova and the first galaxies may have actually formed from a second round of clumping

  • of gas and dark matter as well as dust from the explosions.

  • To be honest, we don't even have a good enough definition of what a galaxy is to know when

  • to stop calling something a cluster of stars and when to start calling it a galaxy.

  • What we do know is that today we have bajillions of galaxies in our universe, none of which

  • existed 13.8 billion years ago, so somewhere in between they must all have been babies.

  • Big gassy babies surrounded by clumps of dark matter.

  • This video was made with the support of NASA's James Webb Space Telescope and the Space Telescope

  • Science Institute. The James Webb Space Telescope is especially sensitive to the infrared wavelengths

  • that light from baby galaxies gets stretched to by the time it arrives in our solar system,

  • so astronomers are excitedly looking forward to using the JWST to learn more about the

  • very first stars and galaxies that ever formed in the universe.

Most things in the universe happen too slowly for us to see them happening. Stars like the

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Where Do Galaxies Come From?

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    Summer posted on 2021/10/08
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