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Transcript of Research Paper
As strange as it seems, most scientists do not believe that galaxies existed from the beginning of the universe. The oldest galaxy ever found was 13 billion light-years away, set in a deep redshift, when Hubble used its Ultra Deep-Field Infrared imager just recently. The galaxy, called UDFj-39546284, is just the predecessor of all the new wondrous galaxies we have in space today. Scientists believe early galaxies, like UDFj-39546284, came into form with little structure. UDFj-39546284 certainly supports this, but other evidence also suggests that the universe was homogeneous, meaning that the universe had an almost uniform structure, which is to say the universe did NOT have much of a structure. There is still debate on why the universe would be that way and how galaxies could form from a smoothly distributed universe, but a theory suggests that as the universe cooled, dark matter and the gas inside them began to cool and condense, supposedly the beginnings of the first galaxies. As said earlier, these “galaxies” were without much structure, and most galaxies were small and existed for not a very long time. However, the locations of the early galaxies influenced the distribution of matter in the universe today, as earlier galaxies have left behind more concentrated areas of matter for new structures. All galaxies, though coming in variety shapes and size, are massive, gravitationally bound systems containing stars, whole star systems and clusters, interstellar clouds, and interstellar medium, the matter in between stars such as gas, dust, and cosmic rays. Galaxies also contain dark matter, a numerous undetectable material that emits no radiation that for few reasons is otherwise effectively theoretical. Galaxies can be 100,000 light years or more in diameter and contain from ten million stars to 100 trillions of stars. Galaxies can be spiral, which rotate around the middle, lenticular, generally old “spiral” galaxies that do not rotate, elliptical, round galaxies with little structure, and irregular, galaxies that do not fit any of the categories. Galaxies are very much unique. No wonder galaxies have been a wonder to mankind since the very first discovery by the Greeks, then Galileo with his telescope, and now to our research with the Hubble Telescope. Galaxies will always perplex us in some way, and we have to keep searching. BILBLIOGRAPHY
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Ironically, not a lot is very sure about today’s visible galaxies either. There are many theories on galactic formation in the past millions of year that we can see. Two theories are very prominent, however. The “top-down” theory suggests that a sudden collapse of an extremely large group of matter could form into a protogalaxy, an early stage of galaxy formation. The “bottom-up” theory suggests that a globular cluster, a small system of already existing stars, is pulled by each other, and then more globular structures pull together to create a galaxy. That galaxy then accretes, or pulls in surrounding matter, and grows in size. Galaxies can take 100 million or more years to form. Galaxies change over time. Galaxies are constantly interacting with each other. Galaxies pull on each other creating larger systems. Galaxies can even collide with one another, either merging or completely the equilibrium of each other. Galaxies are mostly moving away from each other, proven by the high redshift in faraway galaxies. Galaxies have different cycles within each other, and different cosmic activity, making each galaxy unique. One such peculiar example is the “active nucleus,” where a supermassive black hole and an accretion disk, a revolving disk of compressed matter, suddenly shoot out jets of extreme radiation from the core. That red blob is what you are looking for... Accretion Elliptical Spiral Lenticular Irregular Active Nucleus Collision course... Gravity GALAXIES: A WONDER
By Ethan Chan