-------------------- 2769 - ASTRONOMY - learning from most distant stars?
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- It is thought provoking that we can actually see backwards in time. What can we learn from the past?
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- The Hubble Space Telescope has seen the formation of the first stars and galaxies in the early Universe that took place as far back as when the Universe was just 500 million years old.
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- The exploration of the very first galaxies remains a significant challenge in modern astronomy. We do not know when or how the first stars and galaxies in the Universe formed. Especially so soon after the big Bang.
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- Population III stars are these first stars that were forged from the primordial material that emerged from the Big Bang. Population III stars must have been made solely out of hydrogen and lithium. These were the only elements that existed before processes in the cores of stars could create heavier elements, such as oxygen, nitrogen, carbon and iron.
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- The Hubble's Space Telescope observed six distant galaxy clusters from 2012 to 2017 and produced the deepest observations ever made of galaxy clusters and the galaxies located behind them which were magnified by the “gravitational lensing effect“. This new image revealed galaxies that were 10 to 100 times fainter than any previously observed.
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- The masses of foreground galaxy clusters are large enough to bend and magnify the light from the more distant objects behind them. This allows the Hubble telescope to use these cosmic magnifying glasses to study objects that are beyond its nominal operational capabilities.
- “Gravitational lensing” has allowed astronomers to discover galaxies with lower masses than ever previously observed with Hubble. These galaxy distances were corresponding to when the Universe was less than a billion years old.
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- At this earliest point in cosmic time, the lack of evidence for exotic stellar populations and the identification of many low-mass galaxies supports the suggestion that these galaxies are the most likely candidates for the ‘deionization” of the Universe. This period of reionzation in the early Universe is when the neutral intergalactic medium was ionized by the first stars and galaxies.
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- These results have profound astrophysical consequences as they show that galaxies must have formed much earlier than we thought. And that low-mass, faint galaxies in the early Universe are responsible for this reionization.
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- Telescopes are our "time travelers." The farther away an object is, the longer its light takes to reach Earth. Peering back in time requires us to collect “infrared light“. These longer wavelengths in the infrared were initially emitted by stars and galaxies as ultraviolet light more than 13 billion years ago The light waves traveled though the expanding universe and the wavelengths were stretched, or redshifted, into the infrared light.
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- The Hubble Space Telescope has previously created "deep fields" by staring at small areas of the sky for significant chunks of time. The Webb telescope that will be launched this year , 2020, will observe the first galaxies even closer to the Big Bang.
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- Surveys like the Hubble Deep Field have allowed us to map the history of cosmic star formation in galaxies within a half a billion years of the Big Bang all the way to the present in surprising detail.
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- The Webb infrared telescopes will take us further by delivering the unseen. What was the early universe like? There are certainly many data points, but not enough to create an exhaustive census of its conditions. Researchers' knowledge and assumptions are updated frequently, each time a new deep exposure is released.
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- The universe was more compact at this time, which means stars and galaxies could have formed at a greater efficiency. Some models predict we will find 50 galaxies at earlier eras more distant than Hubble can reach, but others predict we will only find a few. In both cases, the data will help us constrain galaxy formation in the early universe.
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- The Webb Telescope Survey hopes to identify an abundance of distant objects, including the most distant galaxies in the universe, early galaxy mergers and interactions, the first massive or supermassive black holes, and even earlier quasars than previously identified.
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- These data will help demonstrate what the structure of the universe was like at various periods from its beginning. More than 13 billion years ago, during the Era of Reionization, the universe was a very different place. The gas between galaxies was largely opaque to energetic light, making it difficult to observe young galaxies. What allowed the universe to become completely ionized, or transparent, eventually leading to the “clear” conditions detected in much of the universe today?
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- The James Webb Space Telescope will peer deep into space to gather more information about objects that existed during the Era of Reionization to help us understand this major transition in the history of the universe.
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- The Big Bang set off a series of events, leading to the cosmic microwave background, the dark ages, the first stars and galaxies, and then to this Era of Reionization. During this period, the gas in the universe transformed from mostly neutral, meaning it was opaque to ultraviolet light, and became completely ionized, which allowed it to be transparent. Ionization means the atoms were stripped of their electrons leading to the "clear" conditions detected in much of the universe today.
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- Many questions remain about this unique time in our universe. For example, what was responsible for converting the gas from neutral to ionized? And how long did it take before the universe became significantly less opaque and much more transparent?
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- We think this happened when ultraviolet light escaped young, forming galaxies. There may be other factors. For example, early accreting black holes may also have emitted ultraviolet light that eventually helped transform the gas.
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- Where the galaxies appear on the sky allows astronomers to examine reionization-era galaxies to see if they are clustered together in the same regions or if they are more isolated.
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- Astronomers have a lot of ideas about what causes galaxies to grow and become more massive, but we need more comprehensive information about these galaxies to fully understand how they initially grew and evolved.
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- The telescopes light spectrum provides invaluable data since to help researchers identify the colors, temperatures, motions, and masses of each target, and provide a much more in-depth look at the chemical makeup of distant objects.
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- Researcher can use the data to analyze the masses of galaxies, galaxy shapes, and photometric redshifts. This tool will take us back to the formation of the Universe. Where did we come from? How did we get here? Stay tuned there is much more to learn.
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- June 29, 2020 2769
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--------------------- Tuesday, June 30, 2020 -------------------------
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