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---------------------- 2350 - How your eyes can see to the edge of the Universe.
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- How far can the eyes see?
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- All the stars we see in the night sky are in our own galaxy, the Milky Way. However in the north-east, just above the horizon, we can see a faint cloud that is the Andromeda Galaxy. It is our neighbor in our Local group of some 24 other smaller galaxies that we cannot see with our naked eyes.
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- Add a telescope and things change. Review 536 has some more interesting data on how far telescopes are reaching in seeing galaxies in the Universe. This review is an update on astronomers currently viewing the edge of the Universe.
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- The hardest thing to put your head around is that these telescopes are looking backwards in time. What you see happened a long, long time ago. With the constant speed of light we can only see what the Universe was like 13,400,000,000 years ago.
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- With the constant speed of light being 186,282 miles per second we can only see that light that has just reached us after traveling for 13,400,000,000 years, During that time what we see has moved away from us even further in an expanding Universe. Today that galaxy we can’t see is 43,000,000,000 lightyears away from us. The rest of the light is still coming and has not reached us yet.
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- It is amazing that astronomers can see almost back to the beginning of the Universe that was not much earlier occurring just 13,800,000,000 years ago. The furthest galaxy seen to date existed just 400,000,000 years after that beginning, called the big Bang.
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- This farthest galaxy recently is named GN-z11. The z11 has some significance as it the ratio of how much the wavelength of light has stretched during that distance traveled to reach our eyes. The wavelength has stretched 11 times longer. The frequency of the light is 11 times slower and has 11 times less energy.
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- We are seeing what the galaxy looked like just 400 million years after it all started in the beginning.
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- The galaxy we are seeing is only 3% of its current age. The human analogy would be looking at 100 year old man when he was only 3 years old. We could only guess what he looks like today at 100.
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- These early galaxies were also 20 times more active than what we see today . Our Milky Way is 20 times less active in churning out new stars. Back then galaxies were closer together. Collisions were more frequent. And, the galaxies were more luminous.
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- The early galaxies were forming stars from clouds of pristine hydrogen and helium gas. There were almost no heavier elements in these early clouds of gas. The gas was falling inward due the pull of gravity. Bright, massive stars were forming. Powerful shock waves were compressing the gas. Smaller galaxies were colliding forming more massive galaxies.
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- These early galaxies were first seen by the Hubble Telescope in 1996 when a time lapsed image was created looking at the same spot in the sky for 100 hours. The image was called the Hubble Deep Field North.
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- This first time lapsed image captured nearly 3,000 small galaxies in a tiny spot in the night sky. The field of view was covering only 1 / 20,000,000 of the sky. The small galaxies ranged from a few spiral galaxies to irregular galaxies and elliptical galaxies. Galaxies were often merging with other galaxies
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- The redshift for this first image was about 6, which represents a time in the Universe about 1 billion years after the Big Bang.
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- Using gravitational wells as magnifying glasses astronomers have viewed galaxies at a redshift of 8 which is viewing images that are 13 billion lightyears away.
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- Astronomers hope to learn how the distribution of early galaxies are linked to the distribution of Dark Matter that they can not see. Its existence is only surmised on its affect on gravity that in turn affects the galaxies that we can see.
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- The most visible galaxies have quasars at their core which are extremely luminous active super massive blackholes.
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- Astronomers are pushing our observational and intellectual horizons ever further outward and back in time. They are viewing younger, and younger galaxies back to their first creations. Astronomers are learning the foundations upon which our Universe is built. Looking backwards in time to discover the beginning of time.
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- Our mind’s eye creates far beyond what we see.
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- Other Reviews to learn more about galaxies:
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- 2340 - How to weigh a galaxy.
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- 2283 - The Universe forms itself into filaments and threads that are all interconnecting with galaxies at the nodes where the filaments come together.
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- 2046 - How galaxies form and grow. This review lists 13 more other reviews about galaxies.
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- May 2, 2019
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-------------------------- Thursday, May 2, 2019 --------------------------
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