- 3018 - GALAXIES - the most distant galaxies? Most of the galaxies in the Universe are “ over the horizon” and beyond what we can see. Astronomers estimate that 98.4% of the galaxies in the Universe lie in the zone that we can never observe. (Unless we find something we can detect traveling faster that the speed of light.)
---------------------- 3018 - GALAXIES - the most distant galaxies?
- The Hubble Space Telescope that takes an image of galaxies that are 13,000,000,000 years back in time.
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---------- What you see is that old, 13 billion years old. The light is that old. The image you see is that young. It is what it looked like 13 billion years ago.
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---------- What you see is moving away from us and has been moving away for that whole duration of time it took for the light to get here.
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--------- The Universe is expanding. The space between galaxies is increasing at an ever accelerating rate. The Galaxy is far further away by now.
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---------- The image we see of the distant galaxies is not what exists today because it took the light 13,000,000,000 years to get here. The photons that reach the Hubble camera are that old. A lot can happen in the time it takes light to make the journey.
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- The Hubble Space Telescope took its pictures using a very long time exposure lasting many days or more. The Hubble camera used CCD’s, charge coupled devices, that can collect photons over that entire time of exposure.
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- Our eyes can not do this. Photons fire nerve cells in the back of our eyes and send the image to the brain. We do not have the ability to collect the photons until the image gets bright enough to see.
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- The Hubble camera has much greater sensitivity and can see very faint objects accumulating photons over a long period of time. Faint objects are very far away and strange things happen while the light is traveling those distances.
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- We do not notice this behavior with galaxies in our neighborhood. If we point our backyard telescope at M87 Galaxy in the Virgo Constellation that light has been traveling 50,000,000 years to reach us. We can say that M87 is 50 million lightyears away. M87 Galaxy is 8 billion years old, so 50 million years is less than 1% of its current age (0.63%). Therefore, the image we get is relatively current. That is probably what the galaxy still looks like today.
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- At that distance of 50 million lightyears M87 is moving away from us at 800 miles per second. This recession velocity will red shift the light a very small amount making the galaxy appear slightly dimmer due to the Doppler Shift of the frequencies of the light.
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- However, this redshift is barely noticeable. M87 is considered as what you see is what you get and that is true for astronomers viewing the 60,000,000 galaxies that are in our neighborhood within 1 billion lightyears away. The galaxies probably are today what they appear to be today. This is not true with the most distant galaxies.
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- The Hubble Deep Field was of images that are the faintest and farthest galaxies 13,000,000,000 light years away ( Galaxy: A1689-zD1). The image we see is really very ancient and not at all like it is today.
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- When the image left this distant galaxy we were much closer together. We were only 3,350,000,000 lightyears apart. The image appears bigger corresponding to a 3 billion lightyear distance rather than the 13 billion lightyear distance we have today. Therefore, the galaxy appears to us to be much closer than it actually is.
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- The galaxy size is bigger, but, it is dimmer than we would expect it to be at 13 billion lightyears distance. Space has been expanding, stretching the lights wavelengths causing a loss of energy and a dramatic redshift and weakening of the light.
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- In fact, it appears dim enough that it should be 263 billion lightyears away at that brightness. The Doppler effect of the expanding Universe causes this ultra-faintness.
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- Over the entire time the light was trying to reach us the Galaxy was moving away from us. Today it is 30 billion lightyears away.
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- If we calculate the very edges of the Observable Universe what distances would we get?
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--------------- The first stars and galaxies were born about 100,000,000 years after the Big Bang.
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-------------- The size of the image we would see would make these galaxies appear as if they were 1,200,000,000 light years away. 1.2 billion lightyears, much bigger than we would expect.
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-------------- The dimness of these galaxies would indicate that they were 1.2 trillion lightyears away. Way dimmer that we could ever detect.
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-------------- The actual distance that the galaxies would be today at the edges of the Universe would be 38 billion lightyears distant.
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- 38 billion lightyears is considered to be the distance to the edge of the Observable Universe.(3.6*10^26 meters) or (2.2*10^23 miles).
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- However, most of the galaxies in the Universe are “ over the horizon” and beyond what we can see. Astronomers estimate that 98.4% of the galaxies in the Universe lie in the zone that we can never observe. (Unless we find something we can detect traveling faster that the speed of light.)
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- Some say the Universe is infinite, but, what does infinite mean? To us it must mean that it is so big we will never see it all. “Never” must mean longer than the life of the Universe, over 13.7 billion years.
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- There must be some things we will just will never know, but, don’t let that stop us from trying.
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February 3, 2021 GALAXIES - the most distant galaxies? 3018
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--------------------- --- Thursday, February 4, 2021 ---------------------------
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