- 3414 - DARK ENERGY - The “Dark Energy Survey” used a modified telescope in Arizona that produced an interim map, which is already the largest three-dimensional map of the universe ever, and the instrument is only about a tenth of the way through its five-year mission.
--------------------- 3414 - DARK ENERGY - The “Dark Energy Survey”
- The Dark Energy Spectroscopic Instrument (DESI) was installed between 2015 and 2019 on the Mayall telescope at the Kitt Peak National Observatory in the Sonoran Desert, about 50 miles west of Tucson, and has been conducting a survey for less than a year.
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- Its purpose is to create larger 3D map of the universe, to yield a better understanding of the physics of dark energy, the mysterious force that is accelerating the expansion of the universe.
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- In the distribution of the galaxies there are huge clusters, filaments and voids. They're the biggest structures of the universe. But within them, you find an imprint of the very early universe and the history of its expansion since then.
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- The new 3D map pinpoints the locations of over 7.5 million galaxies, greatly exceeding the previous record of roughly 930,000 galaxies set by the Sloan Digital Sky Survey in 2008.
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- In this 3D scan of the universe looking out the directions of the constellations Virgo, Serpens and Hercules to distances beyond 5 billion light-years. Each point represents a galaxy, which in turn is composed of 100 billion to 1 trillion stars. Gravity has clustered the galaxies into structures called the "cosmic web," with dense clusters, filaments and voids.
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- DESI collects spectroscopic images of millions of galaxies spread out across about a third of the sky. By examining the color spectrum of the light from each galaxy, scientists can determine how much the light has been "redshifted", stretched toward the red end of the spectrum by a Doppler effect caused by the expansion of the universe. In general, the greater a galaxy's redshift, the faster it is moving away and the farther it is from observers on Earth.
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- Our universe has been expanding since it began with the Big Bang about 13.8 billion years ago, and it is now much larger, at least 92 billion light-years across, than the farthest distances we can see. We are limited to 13.8 billion years because that is oldest light that has reached to date.
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- Scientists with the DESI project hope their 3D map of the cosmos will reveal the "depth" of the sky and help them chart clusters and superclusters of galaxies. Because those structures carry echoes of their initial formation as physical ripples in the material of the infant cosmos, the researchers hope to use the data to determine the expansion history of the universe and its ultimate fate.
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- Measuring the imprint of waves in the primordial plasma, astronomers can actually detect the effect of these waves billions of years later. Scientists used to think that the universe was expanding at a constant rate, or that the combined matter and energy in the universe might eventually cause that expansion to slow down.
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- But observations of powerful stellar explosions called supernovas showed that the expansion is actually accelerating, so scientists coined the phrase "dark energy" to account for this unexpected phenomenon, acceleration needs energy, velocity does not.
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- Calculations now suggest that dark energy makes up around 70% of the total energy in the observable universe. The effects of dark energy are now recognized as the "cosmological constant" that Albert Einstein included in his theory of general relativity; understanding dark energy has become a crucial scientific goal in recent decades.
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- It seems that more dark energy is created as the universe expands, which accelerates the expansion of the universe. Ultimately, the effects of dark energy will determine the destiny of the universe, whether it expands forever, rips itself apart or collapses again in a type of reverse Big Bang.
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- January, 2022, DESI is cataloging the redshifts of about 2.5 million galaxies every month. The team expects to complete the 3D survey map in 2026, by which time the telescope will have observed an estimated 35 million galaxies.
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January 16, 2022 DARK ENERGY - The “Dark Energy Survey” 3414
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