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- Astronomers have discovered the most distant galaxy that can share enough light with us to get a spectroscopy signature. Analyzing the signature can tell us how far away the galaxy is from us and how far its light has traveled. The light has taken 13,100,000,000 years to reach us. That is how old the image is that we are viewing. It existed just 700,000,000 years after the Universe started.
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- The distance to this galaxy reaches 77,028,000,000,000,000,000,000 miles as the crow flies, or as the light travels.
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- The spectrogram uses the Redshift of the element hydrogen to measure the distance. (See Review 1594 to learn how other Redshift measurements are made.)
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- The amount of star formation in this galaxy is amazing. The galaxy produces 300 times the mass of our Sun each year. Compare this with the Milky Way Galaxy that produces only 1 or 2 Solar Masses per year in new stars.
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- The light from the galaxy traveled 13.1 billion lightyears distance. Traveling through that much expanding space has stretched out the wavelength of the traveling photons. When light waves get longer they get shifted towards the red end of the electromagnetic spectrum. When the light left this galaxy it was in the ultraviolet part of the spectrum. When it arrived Earth it was in the infrared part of the spectrum. The amount of Redshift tells astronomers how far the light has traveled and how fast the galaxy is receding from us due to the expanding space in between us.
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- The light emission line that the astronomers identify is hydrogen’s Lyman - alpha line, wavelength of 121 nanometers. Over the distance of expanding space it was stretched out to a wavelength of 1,029 nanometers.
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- The amount the wavelength was stretched was 1029 - 121 = 908 nanometers. The Redshift is the ratio of this amount of shift to the original wavelength at the source.
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--------------------- Redshift = 908 / 121 = 7.5
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- The distance or time in lightyears can be calculated using the equation:
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-------------------- Time = 12.65 + 0.06 ( Redshift )
-------------------- Time = 12.65 + 0.06 ( 7.5 )
-------------------- Time = 13.1 billion years.
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- The Big Bang occurred at 13.82 billion years, so, the image of the galaxy depicted what it was like just 720 million years after the Universe started.
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- The hydrogen atom is the simplest atom composed of only a proton nucleus and one electron. That single electron can exist at several different energy levels in the atom. The electron has a ground state and it can be visualized as having higher energy level orbits above the ground state. The electron can jump between energy states only by absorbing or emitting the exact amount of energy separating the unique energy levels. Every atom has its own unique set of energy levels and number of electrons. When an electron falls from the first energy level to the ground state it emit’s a photon with that unique energy equivalent to the difference in the two energy levels. The unique energy states for hydrogen are known as the “Lyman Series“.
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- The energy of a photon is directly dependent on the frequency. Therefore, ( E1 - E0) is directly proportional to frequency, “f“. To change a proportionality into an equality we need only add a Constant. In this case it is Planck’s Constant, “h”, which is 6.63*10^-34 joule*seconds.
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------------------------ E1 - E0 = h * f
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- The frequency of light is equal to the speed of light, “c”, divided by the wavelength of the light ,”w“.
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------------------------- E1 - E0 = h * c / w
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- For the hydrogen atom the energy level of the ground state, “E0”, is -13.6 electron volts.
- The energy level of the first higher energy is “E1”, -3.4 electron volts.
- The difference energy levels , “ E1 - E0”, is 10.2 electron volts.
- The speed of light is 3*10^8 meters per second. An electron volt is equal to 1.6022*10^-19 joules. Putting these values back in the equation above:
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-------------------- 10.2 = (6.63*10^-34) * (3*10^8) / 1.6022*10^-19 * w
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-------------------- w = 121.6 nanometers.
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- Therefore astronomers know that when the photon left the hydrogen atom in the distant galaxy it left with a wavelength of 121 nanometers. The photons arrive with wavelengths of 1,029 nanometers. The Redshift of the stretched wavelength is 750% The distance it traveled in order to be stretched 750% was 13.1 billion lightyears.
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- With that much space expanding between us the galaxy appears to have a receding velocity 7.5 times faster than the speed of light, 5,332,500,000 miles per hour. Light travels 670,633,500 miles per hour. So, nothing can travel faster than the speed of light. Right?. But, the galaxies are not traveling that fast in space. It is just that there is that much space that is expanding between us. A Redshift of “ 1” or 100% , corresponds to a distance of 12.71 billion lightyears.
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- Redshifts: --------1---------2--------- 3---------4---------5---------6----------7----------8
- BLY: ----------12.71----12.77----12.83----12.89----12.99----13.01---- 13.07 ---- 13.13
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- If the galaxy was actually receding through space at the speed of light then the Theory of Relativity says that time would stop, and the distance would shrink to zero.
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-------------------- Time at light speed = time ( 1 - v^2 / c^2 )^½
-------------------- If: v^2 = c^2
-------------------- then: time = zero
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- Let’s say our spaceship is traveling towards our nearest star, Alpha Centauri, 4.37 lightyears away. We are traveling at 99.995% the speed of light.
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------------------ Distance = 4.37 lightyears * ( 1 - v^2 / c^2 )^½
------------------ Distance = 4.37 * ( 1 - (0.99995) )^½
----------------- Distance = 0.0437 lightyears
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- The spaceship has shrunk by a factory of 100 and the distance to the star has shrunk to 0.0437 lightyears. Traveling at the speed of light has its advantages. But, that is not what is happening with galaxies in the expanding Universe. Seeing backwards in time is strange enough without getting in to the Theory of Relativity.
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RSVP, please reply with a number to rate this review: #1- learned something new. #2 - Didn’t read it. #3- very interesting. #4- Send another review #___ from the index. #5- Keep em coming. #6- I forwarded copies to some friends. #7- Don‘t send me these anymore! #8- I am forwarding you some questions? Index is available with email upon request. Some reviews are at http://jdetrick.blogspot.com Please send feedback, corrections, or recommended improvements to: jamesdetrick@comcast.net. ---- “Jim Detrick” -- www.facebook.com, -- www.twitter.com, -- 707-536-3272 Friday, November 1, 2013
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