U.S. detector installed with 5,000 “eyes” to explore cosmic expansion


WASHINGTON, Oct 29 (XINHUA/APP):A new instrument mounted atop a telescope in the United States has aimed its robotic array of 5,000 fiber-optic “eyes” at the night sky to explore the mystery of dark energy that makes up about 68 percent of the universe.

It was the first test of the Dark Energy Spectroscopic Instrument (DESI), which are designed to capture the first images of a unique view of galaxy light.

The instrument can 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 dark energy is believed to drive the accelerating expansion of the universe.

DESI was installed in February 2018 on top of a 45-year-old telescope at Kitt Peak National Observatory in Arizona. The start of its final testing is a milestone towards the formal start of observations in early 2020, according to a news release on Monday by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, who supported the project.


The engineers have installed a focal plane on top of the 4-meter primary mirror of the telescope, carrying 5,000 robotic positioners that swivel in a choreographed “dance” to individually focus on galaxies. Each of the positioners holds a light-gathering fiber-optic cable that is about the average width of a human hair, serving as DESI’s eyes.

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 3D map of the universe.

DESI will repeatedly map 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, and provide a precise measurement of the universe’s expansion rate.

Gravity slowed this rate of expansion in the early universe, but dark energy has since been responsible for speeding up its expansion, according to researchers.

“By looking at that map, we can see how the structure of the universe has changed with cosmic time, and that gives us an idea of how fast the universe is expanding at any given time,” said Fan Xiaohui, a professor of astronomy from Steward Observatory at University of Arizona.

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