Harvard Smithsonian's New DESI Instrument for Studying Dark Matter is a Robotic House of Horrors with 5000 Eyes

Wednesday, 30 October 2019 - 10:43AM
Astronomy
Wednesday, 30 October 2019 - 10:43AM
Harvard Smithsonian's New DESI Instrument for Studying Dark Matter is a Robotic House of Horrors with 5000 Eyes
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The Dark Energy Spectroscopic Instrument – or DESI for short – is, as Emperor Palpatine so aptly put it, "fully armed and operational." A team of Arizona scientists just tested it to great success, according to a recent press release from the Center for Astrophysics Harvard & Smithsonian.


"Most of the universe's matter and energy are dark and unknown, and next-generation experiments like DESI are our best bet for unraveling these mysteries…I am thrilled to see this new experiment come to life," said DESI Director Michael Levi of the Department of Energy's Lawrence Berkeley National Laboratory.


With 5,000 fiber-optic eyes, DESI could be a contender for your last-minute Halloween costume, but these "eyes" are more function than form. Each holds a fiber-optic cable about the width of a human hair. Placed end-to-end, they would stretch 150 miles. They are calibrated to measure the light from a defined set of galaxies and then translate that light into colors.


DESI's components are designed to 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. The release explains it this way:


"By measuring these spectra, DESI can determine how fast each galaxy is moving away from Earth. Because the universe is expanding, galaxies are moving away from us, with more distant galaxies moving faster. This motion stretches the wavelength of the light we receive, much as the sound of a fire engine's siren shifts to lower tones as it moves away from us."


On a good day, DESI can churn out information for 5,000 galaxies every 20 minutes.




(DESI's view of the night sky. Each dot represents a robotic eye with a single fiber-optic cable. Credit: DESI Collaboration)


Based on these models, DESI will construct a 3D map of the Universe. Scientists estimate that it will shoulder 20x the workload of any instrument before its time, charting 35 million galaxies and over 2 million quasars. By analyzing the speed at which these objects are moving away from Earth, scientists can then use this information to fill in the gaps of our knowledge on dark energy.


With this unprecedented look into deep space, scientists will be able to get a closer look at dozens of other phenomena that have remained shrouded in mystery. According to Douglas Finkbeiner from the Center for Astrophysics | Harvard & Smithsonian, "A beautiful aspect of DESI is the ability to combine precision calibration and novel statistical tools with the raw size of the data set. I look forward to the DESI opportunity not just to study dark energy, but the Milky Way, galaxies, quasars, and everything in between."


 

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