- 3559 - UNIVERSE - what is the earliest galaxy? Most galaxies after the birth of the universe were small, compact, dwarf galaxies. A consequence of existing just a few hundred million years after the Big Bang, when the universe was hotter and denser than it is today. These little galaxies were also less bright than galaxies today, with less room for big, luminous stars.
--------------------- 3559 - UNIVERSE - what is the earliest galaxy?
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- What is a “naturally occurring telescope” ? We used one to peer at a very distant, gargantuan star, estimated to be an incredible 50 times the mass of our Sun. The telescope used “gravitational lensing” with the Hubble Space Telescope. The faraway star is dubbed “Earendel”. It was only born about 900 million years after the Big Bang.
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- Telescopes are constrained by the amount of light they can gather. Distant objects are therefore very difficult to see, as there is less light to collect from those objects. That light has spread out across the Universe in all directions.
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- Gravitational lensing allows astronomers to use a massive foreground object, in this case, stars within a star cluster, to bend and focus the light from something in the background. Massive objects in space deform space-time around them, allowing them to act like a magnifying glass, amplifying light from the background object. The effect was first predicted by Albert Einstein’s theory of general relativity.
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- Follow-up data from Webb in infrared light will scrutinize the star’s spectrum signature of light. Spectral data allows astronomers to look for individual elements within the star. Learning about the star’s composition will tell astronomers about the star’s life history, age and where the star fits in with the early evolution of the universe.
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- Webb’s wavelengths go much deeper into infrared than Hubble. It also flies further in space and away from the stray light of Earth, at a stable gravitational zone known as Lagrange Point 2. Webb’s infrared eyes, its deep space location, and its higher definition will all contribute to gathering a detailed spectrum of this distant star.
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- Webb’s mandate will be to peer across 13.5 billion years of time to learn about the first stars and galaxies that were formed. The infrared vision makes it an ideal observatory to examine these early stars, which are receding away from us due to the ongoing expansion of the universe. The stars are highly redshifted, meaning that their light is shifted towards the red edge of the spectrum due to the stars’ light stretching as they recede away from us..
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- NASA plans to launch the “Nancy Grace Roman Space Telescope” in 2027 to image wider star fields than Hubble, with equivalent resolution. If a magnifying star passes across a huge background structure like a galaxy cluster the star provides a glimpse of what the cluster looks like in high definition including the granularity of normal matter and dark matter, both of which are important to learning about a galaxy’s evolution or history.
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- “HD1” is a candidate galaxy that may be the most distant astronomical object we have ever seen. HD1 is so distant that it extends all the way back to a time when the universe was less than a billion years old.
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- The galaxy is strange for something that is 13.5 billion light-years away. It is brighter than it should be. It could be the key to understanding the early universe, as well as the first stars and first galaxies.
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- High redshift refers to how light appears in the universe. Something exhibiting blueshift is coming toward us, while redshift means it is moving away from us. An object with a high redshift is “very far away” from us.
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- The two galaxy candidates were at extremely high redshift, called HD1 and HD2. It took 1,200 hours of observing the sky using four powerful observatories: The Subaru Telescope, VISTA Telescope, UK Infrared Telescope, and Spitzer Space Telescope.
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- HD1 and HD2 could be among the galaxies that spewed ionized hydrogen gas into the interstellar medium, leaving space “clear” as we see it today. Before this outpouring of gas, the universe can be thought of as more cloudy and opaque.
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- HD1 appears to be very bright, meaning that it’s likely one of two exceptional possibilities: A small galaxy packed with a population of bright first-generation stars, or a supermassive blackhole consuming matter surrounding it.
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- Because they were such low mass, the effects of stars forming in them could have caused a lot of damage in the sense of pushing gas out of them. HD1 and HD2 are at redshift 13, which roughly corresponds to 13.5 billion light-years away or just 300 million years after the universe formed. A redshift of 13 means the universe was smaller by a factor of 14 at the time. This is an order of magnitude smaller.
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- If this galaxy was rife with star formation at a time that kind of activity was supposed to be rare forcing astronomers to rethink some of their theories of the early universe. All large galaxies are believed to have supermassive blackholes at their center, but how these behemoths form is poorly understood.
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- If HD1 has a supermassive blackhole, then it would likely be a “quasar“. A supermassive blackhole at the center of a galaxy rapidly devouring matter around it and then ejecting it out in bright light.
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- An X-ray telescope could look at HD1 and determine its energy output. This would tell scientists about the nature of the object, and confirm if it’s a blackhole.
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- The James Webb Space Telescope is equipped to stare at the early universe. It might be able to observe HD1 and other high redshift galaxy candidates and get a sense of their spectra. That could give clues as to its structure. If it remains a single point source, it’s very likely a bright quasar instead of a galaxy rife with stars.
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- Presuming that these observations confirm the supermassive blackhole theory, the quasar’s brightness can also tell astronomers a lot about the mass of the blackhole. If the star-filled galaxy theory holds up, we can do a similar “weigh-in” and infer the number of stars it would need to hold to emit the light we see today.
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- What Webb reveals could be a major puzzle piece to reveal the true nature of the early universe.
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April 26, 2022 UNIVERSE - what is the earliest galaxy? 3559
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