Berkeley Lab researchers design array of robots to seek distant galaxies

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Researchers at the Lawrence Berkeley National Laboratory have designed robots to pinpoint galaxies billions of light-years away, getting a step closer to understanding the expansion of the universe.

ProtoDESI is a testing and calibrating prototype of the Dark Energy Spectroscopic Instrument, or DESI, an array of 5,000 robots that will help scientists make a three-dimensional map of the universe. The final array will provide insight into the nature of dark energy and the distance between objects in our universe, as well as create a three-dimensional map of the universe.

ProtoDESI is a smaller array of 10 robots that will test that the system accurately pinpoints stars, but will not collect data. Each small cylindrical robot contains a fiber optic cable that records the light from star systems and two motors that swivel the cables in order to pinpoint the star systems.

“This will enable us to create the largest and most accurate map of the universe to date, which will in turn shed some light on its mysteries,” said Uros Seljak, director of the Berkeley Center for Cosmological Physics, in an email.

Each point of light DESI records contains hundreds of millions of stars up to 11 billion light-years away, according to Parker Fagrelius, a UC Berkeley graduate student who is managing the ProtoDESI project at Berkeley Lab. In August, Fagrelius and other scientists will go to the Mayall telescope in Arizona to install and monitor ProtoDESI, using any information they learn to make changes to DESI.

“It will give the scientific team great confidence that the DESI team is capable of making the measurements it’s designed to make,” Fagrelius said.

The map created will give scientists information about cosmic events that took place long ago due to the distance of some of the stars, according to Fagrelius. Scientists will use measurements of “angular size” to measure the distance between galaxies, which will provide insight into “ripples” in the early universe.

“We’re basically looking into the past,” Fagrelius said. “It will give us hints about whether or not dark energy has changed over time.”

The previous most accurate pinpointing system, BOSS, required researchers to create a metallic plate with holes, for each star system under observation, every night. Once the metal plate was attached to the telescope, researchers manually inserted the fiber optic cables into each hole.

DESI robots will have the ability to pivot autonomously in order to examine new configurations of stars every night.

“BOSS did on the order of two million targets; DESI wants to do 10 times that,” said Joseph Silber, a staff engineer at Berkeley Lab and one of the designers of the robots.

Researches have built eight generations of the prototype over roughly five years for the robots, refining the process each time. Silber said it was complicated to calibrate the robots so that their heads would not bump into each other.

The DESI array, expected to be installed in Arizona in late 2018, will be in place for five years, gathering data every night.

Contact Mira Chaplin at [email protected].