Berkeley Lab constructs instrument for observing galaxies

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An instrument attached to the top of a telescope in Arizona, primarily operated and constructed by the Lawrence Berkeley National Laboratory, has aimed its 5,000 fiber-optic “eyes” at the night sky to aid researchers’ observations of the galaxies.

The Dark Energy Spectroscopic Instrument, or DESI, is mounted on top of the Nicholas U. Mayall Telescope at the Kitt Peak National Observatory near Tucson, Arizona. The DESI allows for exploration of the galaxy’s dark energy, which comprises about 68% of the universe, according to a Berkeley Lab news release. 

The DESI is constructed to preselect sets of galaxies, calibrating how much the universe expanded as light travels to Earth, going through 5,000 galaxies every 20 minutes.

“After a decade in planning and R&D, installation and assembly, we are delighted that DESI can soon begin its quest to unravel the mystery of dark energy,” said DESI Director Michael Levi of Berkeley Lab in a statement.

Observing quasars, one of the brightest objects in the universe, with the DESI allows researchers to look into the universe’s past, its beginnings and early developments. 

The DESI provides accurate measurements of the universe’s expansion rate. According to the news release, “Gravity had slowed this rate of expansion in the early universe, though dark energy has since been responsible for speeding up its expansion.”

Lori Allen, director of Kitt Peak National Observatory, said in a statement that the DESI elevates the use of a regular telescope.

“With DESI we are combining a modern instrument with a venerable old telescope to make a state-of-the-art survey machine,” Allen said in the statement. 

The DESI’s focal plane — the instrument’s eyes — allows it to target greater than 20 times more objects than previous experiments, according to the release. The focal plane consists of 5,000 robotic positioners that “dance” to individually focus on galaxies. It only takes about 10 seconds for the positioners to move from each targeted galaxy. 

A unique feature of the DESI is its spectrographs, which allow it to obtain accurate distance measurements of galaxies across a range of colors. The spectrographs allow the DESI’s focal planes to view faraway galaxies, according to the news release. 

The University of Michigan made a portion of the robotic positioners, including spares. The positioners were delivered to Berkeley Lab for installation and delivered to the Kitt Peak National Observatory to mount onto the telescope.

Gregory Tarlé, a professor at the University of Michigan, said in a statement that he is excited about the prospect of DESI’s new discoveries.

“I want to find out what the nature of dark energy is,” Tarlé said in the statement. “We finally have a shot at really trying to understand the nature of this stuff that dominates the universe.”

Contact Marc Escobar at [email protected] and follow him on Twitter at @mescobar_dc.