DESI’s quest to map the expanding universe begins: NewsCenter
Rochester researchers are key members of an international collaboration to create a 3D map of the universe, which will help unravel the mysteries of dark energy.
A five-year quest to map the universe and unravel the mysteries of dark energy will officially begin this month as the Dark Energy Spectroscopy Instrument (DESI) begins its main study to capture and study light from 35 million galaxies and 2.4 million quasars – the brightest objects in the universe – through an area of the sky in the northern hemisphere.
Researchers will use the data collected by DESI to travel 12 billion years of 13.8 billion year history of the universe. The goal is to unravel more clues to the mystery of dark energy – a hypothetical entity that makes up over 70% of the universe and is believed to be the engine behind the expansion of the universe – and ultimately create the most detailed 3D map of the universe ever.
DESI is an international scientific collaboration involving 75 institutions in 13 countries. DESI participants include researchers from Rochester University cosmology group, an interdisciplinary group that includes professors, postdoctoral research associates, graduate students, and undergraduates in physics, astronomy, data science, and computer science.
The project will measure 10 times more galaxy spectra than ever before.
“When I was in high school, it took years to build catalogs of 100,000 spectra of galaxies,” says Segev BenZvi, associate professor of physics and member of the Rochester Cosmology Group. “Today, DESI can record so many spectra in a single night with good viewing conditions. It is these high statistics that allow us to make a big leap in the precision of general relativity and dark energy measurements.
What is Dark Energy Spectroscopic Instrument (DESI)?
The DESI instrument resides in the modernized Mayall Telescope at the National Science Foundation’s Kitt Peak National Observatory near Tucson, Arizona. The instrument incorporates new optics that increase the telescope’s field of view and includes 5,000 robot-controlled optical fibers to collect spectroscopic data from an equal number of objects in the telescope’s field of view.
The Rochester Group is responsible for ensuring that 5,000 fibers are optimally pointed to their targets, by developing and troubleshooting software to monitor the fibers.
Rochester’s historic strengths in optics and physics
Rochester’s strong research history in optics, physics, and probing the mysteries of our universe makes DESI an ideal project for the cosmology group.
To prepare for DESI, members of the cosmology group, co-directed by Regina demina, professor of physics, have developed new algorithms to study the accelerated expansion of the universe, the growth of structures in galaxy clusters and the presence of dark matter on a galactic scale.
“Fast and smart algorithms are the key to understanding big data,” Demina says. “We hope to use our algorithms to test the distribution of matter in the early universe, which will help shed light on the processes that drove its expansion moments after the Big Bang, also known as inflation. Even particle accelerators that probe the state of the universe that was a picosecond old cannot reach this depth. “
DESI restarts after COVID break
The official start of DESI’s five-year investigation follows an eight-month hiatus on the project, due to the COVID-19 pandemic. After the project restarted in late 2020, travel restrictions prevented researchers from visiting Kitt Peak, so the Rochester group switched to making remote observations.
BenZvi, for example, has set up a bank of monitors in his home office and has helped operate the instrument from Rochester every two weekends for the past four months, while testing the DESI custom instrumentation.
“While not as adventurous as being at Kitt Peak, it’s still a lot of fun watching the data pop up in real time,” says BenZvi. “It’s amazing how quickly the instrument accumulates new data.”
Each night, when the telescope is moved to a target position, the optical fibers align to collect the light from the galaxies as it is reflected by the telescope’s mirror. From there, the light is fed into a bank of spectrographs and CCD cameras for further processing and study.
The spectra collected by DESI are the components of light corresponding to the colors of the rainbow. Their characteristics, including wavelength, reveal information such as the chemical composition of the objects observed as well as information about their relative distance and speed.
As the universe expands, galaxies move away from each other and their light is shifted to longer, redder wavelengths. The farther away the galaxy, the greater its “redshift”. By measuring the redshifts of galaxies, DESI researchers will be able to create a 3D map of the universe.
DESI is supported by the US Department of Energy Office of Science and the National Energy Research Scientific Computing Center, a user installation of the DOE Office of Science. Additional support is provided by the US National Science Foundation, the Science and Technologies Facilities Council of the United Kingdom, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, the French Alternative Energies and Atomic Energy Commission (CEA), the Conseil National Science and Technology of Mexico, the Spanish Ministry of Economy and by DESI member institutions.
Members of a University of Rochester cosmology group who are a key part of a multi-institutional effort to create the most detailed 3D map of the universe yet are anxiously awaiting the launch of the instrument later this year in Arizona.
Category: Scientific technology