Berkeley Lab leads installation of instrument to solve dark energy mystery

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On Feb. 12, 500 pencil-sized robots were ready to be installed on the Nicholas U. Mayall Telescope as the first part of an instrument that could provide new insight into the secrets of the universe.

The international collaboration to install the Dark Energy Spectroscopic Instrument, or DESI, on Mayall Telescope at Kitt Peak National Observatory is being led by the Lawrence Berkeley National Laboratory. DESI is a multi-object spectrograph that will analyze the spectra of deep-space objects for signals that tell how distant an object is and how fast it is moving away.

DESI’s measurements could provide significant contributions to the studies of dark matter and dark energy, the two big mysteries in the physics and astronomy communities, according to David Schlegel, a scientist for the DESI project and the Berkeley lab.

According to DESI Director Michael Levi, DESI will take 10,000 shots of the sky over the course of five years “to make a 3D map of the universe.”

Each pencil-sized robot contains a computer-controlled fiber optic cable that points at and takes the spectra of identifiable galaxies and quasars. The different wavelengths of light emitted are analyzed for signs of redshift, which indicate that the universe is expanding and objects are moving farther away more quickly.

Another major goal of the project is to learn more about the role of dark energy in the expansion and composition of the universe.

“We’ll discover new things that we haven’t thought of,” Schlegel said. “When you make a huge leap in what you can do, there are … new discoveries found.”

The team, comprised of more than 400 scientists and 120 construction members around the world, is currently outfitting the Mayall Telescope in Arizona’s Kitt Peak National Observatory with DESI. The Mayall Telescope was chosen for its ability to support the 9-ton instrument.

One major change to the Mayall Telescope is the new corrector, which is comprised of six lenses that are each 1 meter in diameter. In addition, there will be 10 spectrographs, which analyze the data received from the focal plane. When DESI’s 10-wedge focal plane is completed, there will be a total of 5,000 small robots taking in a section of the universe in one shot.

“One of the beauties of (DESI) is that people can take so many spectra at once,” said Joan Najita, a chief scientist at the National Optical Astronomy Observatory. DESI’s ability to take large-scale observations will make maps of the universe more detailed.

The installation is projected to be finished in April 2019, with the first observations scheduled for September 2019. Parker Fagrelius, a campus physics graduate student, led the first on-sky testing of DESI subsystems on the Mayall Telescope in summer 2016.

DESI will continue to be an important resource for students and researchers alike in the years to come, opening the scientific community to new discoveries in the sky, the researchers said.

“Working on DESI has been an excellent opportunity for me as a graduate student,” Fagrelius said in an email. “This is really the first step towards making DESI a reality rather than just a well thought out idea.”

Contact Andreana Chou at [email protected] and follow her on Twitter at @AndreanaChou.