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-------------------- 2463 - DESI - new telescope to explore the Universe
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- DESI’s components automatically point at preselected sets of galaxies, gather their light, and then split that light into narrow bands of color to precisely map their distance from Earth and gauge how much the universe expanded as this light traveled to Earth.
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- In ideal conditions DESI can cycle through a new set of 5,000 galaxies every 20 minutes. DESI’s 5000 spectroscopic “eyes” can cover an area of sky about 38 times larger than that of the full moon.
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- Each one of the robotically controlled eyes can fix a fiber-optic cable on a single object to gather its light. The gathered light collected from a small region in the Triangulum galaxy by a single fiber-optic cable (red dot) is split into a spectrum that reveals the fingerprints of the elements present in the galaxy and aid in gauging the distance to the galaxy.
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- Like a powerful time machine, DESI will peer deeply into the universe’s infancy and early development, up to about 11 billion years ago, to create the most detailed “3-D map” of the universe.
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- By repeatedly mapping the distance to 35 million galaxies and 2.4 million quasars across one-third of the area of the sky over its five-year run, DESI will teach us more about dark energy. Quasars are among the brightest objects in the universe, they allow DESI to look deeply into the universe’s past.
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- DESI will provide very precise measurements of the universe’s expansion rate. Gravity had slowed this rate of expansion in the early universe, though dark energy has since been responsible for speeding up its expansion.
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- Most of the universe’s matter and energy are dark and unknown. With DESI astronomers are combining a modern instrument with a venerable old telescope to make a state-of-the-art survey machine.
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- DESI’s focal plane carries 5,000 robotic positioners that swivel in a choreographed “dance” to individually focus on galaxies, is at the top of the telescope. These little robots each hold a light-gathering fiber-optic cable that is about the average width of a human hair.
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- It takes about 10 seconds for the positioners to swivel to a new sequence of targeted galaxies. With its unprecedented surveying speed, DESI will map over 20 times more objects than any predecessor experiment.
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- The focal plane, which is comprised of a half-million individual parts, is arranged in a series of 10 wedge-shaped petals that each contain 500 “positioners” and a little camera to help the telescope point and focus.
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- The focal plane, corrector barrel, and other DESI components weigh 11 tons, and the Mayall telescope’s movable arm that DESI is installed on weighs 250 tons and rises 90 feet above the floor in the Mayall’s 14-story dome.
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- The collection of spectrographs are designed to split up the gathered light into three separate color bands to allow precise distance measurements of the observed galaxies across a broad range of colors.
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- These spectrographs are designed to measure redshift, which is a shift in the color of objects to longer, redder wavelengths due to the objects’ movement away from us. Redshift is analogous to how the sound of a fire engine’s siren shifts to lower tones as it moves away from us.
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- To connect the focal plane with the spectrographs, which are located beneath the telescope, DESI is equipped with about 150 miles of fiber-optic cabling.
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- Astronomers can actually map the history of the universe and see what the universe is composed of by looking at very different objects from different eras.
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- November 3, 2019 2463
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--------------------- Monday, November 4, 2019 --------------------
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