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---------------------- 1890 - A supernova far away betrays Dark Matter.
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- In a distant spiral galaxy 9.5 billion lightyears away the light started from a supernova explosion. The explosion was too dim for astronomers to see directly. It was “redshifted” into the infrared spectrum due to the extreme distance of expanding space in which the light traveled.
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- The Earth and Moon were just forming 5 billion years after this event. And, at about the same time the light from this supernova encountered an enormous cluster of galaxies that were in our line of sight. The enormous gravity bent the light beams as they passed by and through this gravity well created by warped space-time.
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- The bent light beams just happened to focus on the planet Earth 4.5 billion light years away. It was like a gigantic magnifying glass that magnified the images of the spiral galaxy by 100 times. There were multiple images as the bent light beams took different paths around the cluster on their way to Earth. Astronomers were able to detect the supernova in the magnified images starting November 2014. The four images were separated by mere days on their arrival.
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- These images were bent around the boundary of the immense galaxy cluster. That allowed astronomers to calculate the mass of the cluster. Most amazing of all they calculated that this same image traveling the direct route through the cluster’s deepest gravity well would not arrive until a year later, November 2015.
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- The Hubble Space Telescope began looking one orbit per month hoping to spot this same supernova again. Einstein’s equations were precise. They calculated the precise way the light interacted with the gravitational lens. It is counter- intuitive but it took a year longer for the light to escape the gravity will through the cluster center and in our direct line of sight.
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- It was the supernova that allowed astronomers to using the timing of this event in their calculations. Without it the images would not be unique enough to identify that they originated in a single event 9.5 billion years ago. What are the chances that this scenario could actually come together to allow such a prediction?
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- In November 1915 Albert Einstein published his new theory of gravity. He predicted that light would bend as it took the shortest path through warped space-time as it moved past a massive object. In 1919 Arthur Eddington detected this phenomena as background stars shifted as their light passed by an eclipsed Sun.
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- In 1937 Fritz Zwicky predicted multiple images of a single galaxy would occur due to gravitational lensing from a foreground mass. In 1967 Sjur Refsdal, a Norwegian astronomer, showed that gravitational lensing calculations could map the mass in the lensing galaxy, or cluster of galaxies. These calculations could also be used to define the expansion rate of the Universe if the background galaxy contained an exploding star.
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- In 1979 the first cosmic gravitational lens was observed. In 2013 the Hubble Telescope was assigned a galaxy cluster target, MACSj1149. In November 2014 Hubble spotted the first multiple images of the background galaxy directly behind his target. And, with unbelievable luck also spotted the supernova and began plotting its light curve as it brightened to maximum and slowly faded in its intensity.
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- The supernova was hydrogen- rich representing among the first stars formed after the Big Bang. It was a blue supergiant star, and unlike a Type 1a supernova, it could not be used as a “ standard candle” to calculate its distance. Instead the distance calculations were made using the method of “ redshifts” due to the expanding space in which the light traveled.
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- Hubble is still watching this distant galaxy through the gravitational lens. Gravity alone offers a factor of 100 times magnification power. But, the supernova light is fading fast and will soon be out of sight. Astronomers have serendipity to thank for the enormous amount of data collected. New knowledge will surely come out about Dark Matter, galaxy formations, and the expansion of the Universe. Who knows? An announcement will be made shortly, stay tuned.
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- Request these Reviews to learn more about gravitational lensing:
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- #1534 - The diameter of the gravity lens ring is directly proportional to the mass. Another calculation the mass of the galaxy cluster is measured by the orbital velocity of the galaxies about the center of gravity. Example calculations are provided.
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- #1885 - Gravity a property of space and time. Lists a dozen more reviews about gravity, space, and time.
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