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- 2049 - The furthest star we can see gets the help of intervening galaxies that act as gravitational magnifying lenses. Starting with our own Milky Way Galaxy astronomers are trying to create a 3-D map of stars and galaxies. What they are seeing is a cosmic web interconnecting all the galaxies with massive voids of space in between the web of galaxies.
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------------------------ 2049 - The Expanding Universe.
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- The furthest star we can see gets the help of intervening galaxies that act as gravitational magnifying lenses. The star is called Icarus and we see it when it was 4 billion years after the Big Bang.
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- That is the furthest star. We can see galaxies , groups of stars, much further back in time. The gravitational lens was created by a massive cluster of galaxies that were 8.8 billion lightyears after the Big Bang and 5 billion lightyears from Earth. The gravity lens boosted the stars brightness by a factor of 2,000 times.
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- Icarus is a bright blue super giant star. It is much bigger than our Sun and hundreds of thousands of times brighter. It took 9 billion years for its light to reach us. Galaxies that we can see further away cannot resolve individual stars.
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- Starting with our own Milky Way Galaxy astronomers are trying to create a
3-D map of stars and galaxies. What they are seeing is a cosmic web interconnecting all the galaxies with massive voids of space in between the web of galaxies.
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- As of 2013 astronomers have catalogued over a billion objects in our own galaxy. Starting with our own star that was first measured to be 28,700 lightyears from the galaxy center. They then measured over 200,000 star’s orbital speed about the center.
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- The Sun moves around the center at 536,865 miles per hour. This new data put the Sun’s distance at 25,767 lightyears from galaxy center.
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- When measurements made of distances to other galaxies they found some 2,000 galaxies all the same distance away. Named this the Virgo Cluster and measured it to be 55 million lightyears from Earth.
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- To measure these distances astronomers look at light spectra. The expansion of the Universe stretches the galaxy’s light shifting it toward the red end of the spectrum. The amount of shift is used to calculate the distance to the galaxy. Distance and position are then used to create a 3-D map.
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- The galaxy clusters clump together in cylindrical filaments and walls of galaxies to form a supercluster, the Virgo Supercluster. We live in the Local Group that is part of this cluster.
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- This supercluster of galaxies is falling toward a region in the southern sky at 370 miles per second. 1,332,000 miles per hour. Astronomers have yet to find the gravity source, but they call it the Great Attractor. After measuring the motion and velocity of 8,000 galaxies that are all moving toward this same place in space.
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- The supergiant star lives more than halfway across the observable universe. It's much bigger than our own Sun and hundreds of thousands of times brighter. Despite its brilliance, it still took nine billion years for its shining light to reach Earth.
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- The star’s brilliance was given a boost due to gravitational lensing. This is when gravity forms a massive celestial object that acts like a magnifying glass, bending and amplifying the light from objects that are behind it.
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- Five billion light-years from Earth, a galaxy cluster sits between our planet and Icarus. Icarus was magnified when a star in that galaxy cluster moved in front of the more distant star. Icarus is at least a hundred times farther than the next nearest star. Astronomers have observed galaxies at greater distances but have been unable to pick out their individual stars.
- The Big Bang happened about 13.8 billion years ago. Icarus is so old that the light observed was generated when the universe was just 30 percent of its current age.
Icarus's bright glow is helping astronomers test hypotheses about dark matter. One theory suggests that dark matter is made of primordial black holes, hypothetical objects that would have formed just after the Big Bang. The light fluctuations seen from Icarus make this hypothesis unlikely because their observations would not have been possible with intervening black holes.
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- The Milky Way galaxy is moving 1.2 million miles per hour being gravitationally pulled by a mysterious Great Attractor. In between the giant super clusters of galaxies is a huge intergalactic void. Our solar system sits on then opposite side of our galaxy preventing direct observation of the Great Attractor . In attempts astronomers have discovered over 800 new galaxies in that same part of the sky.
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- These galaxies are somehow moving faster than the universe is expanding. The distribution of galaxies appears to have regions of under- dense dark matter that repels mass and over- dense regions of luminous galaxies that attract mass. The repeller region spans 1.7 billion lightyears of space.
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- Astronomer are using a new technique to measure the super void. They measure the photon’s changes in velocity as they pass through the void to determine the rate of expansion of the universe. (See Review 1896 to learn how these measurements are made).
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- The Cosmic Microwave Background radiation is a snap shot of space when the universe was 380,000 years old. Since then the universe has cooled from 3,000 Kelvin to 2.75 Kelvin, that is -455 degrees Fahrenheit, the average temperature of space today.
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- This ultraviolet temperature that has cooled to microwave background temperature is amazingly uniform on the grandest scale. However , at a closer look to one part in 10,000 variations appear. That is when the giant void can be seen extending 1,800,000 lightyears across. The average voids between galaxies is only 500,000 lightyears across.
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- As the background light photons pass through this void they lose energy caused by the gravitational pull. The speed of light remains constant but the frequency lowers and the wavelength stretches. The photons loose energy.
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- These same photons at the opposite side of the void experience the opposite effect. The photons gain energy with the pull of gravity from the mass at the other edge of the void. This energy change can be correlated to the temperature cooling then the temperature heating as the photons pass through the giant void.
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- The net effect does not take into account the expanding space during the travel. This effect means the photons can not regain all the energy they lost after entering the void. This effect is called the Integrated Sachs-Wolfe Effect.
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- Astronomers want to accurately determine the acceleration rate of the expanding universe. Measuring a void should be much easier than measuring through a cluster of galaxies. The hope for this research is that astronomers can learn some explanation for dark energy that appears to be the power source expanding the universe. Not only expanding but mysteriously the repulsive force is accelerating the expansion. Who knew? Expanding your mind to keep up with astronomy. Amazing stuff!
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------------------------- Friday, April 6, 2018 --------------------------------
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