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From Cosmos, May 6, 2019: An extensive analysis of four different phenomena within the universe points the way to understanding the nature of dark energy, the Dark Energy Survey reveals.
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By developing clever theories and conducting experiments with particle colliders, telescopes and satellites, physicists have been able to wind the film of the universe back billions of years—and glimpse the details of the very first moments in the history of our cosmic home. Take a (brief) journey through the early history of our cosmos.
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From Science Channel's Space's Deepest Secrets, April 23, 2019: In an episode of this television series, Fermilab scientist Craig Hogan discusses the Holometer and his theories of the holographic universe.
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The Dark Energy Spectroscopic Instrument seeks to further our cosmic understanding by creating the largest 3-D map of galaxies to date. Below is a press release issued by Lawrence Berkeley National Laboratory announcing first light for the optical lenses of this extraordinary instrument. The U.S. Department of Energy’s Fermi National Accelerator Laboratory is a key player in the construction of this instrument, drawing on more than 25 years of experience with the Sloan Digital Sky Survey and the Dark Energy Survey.

Fermilab contributed key elements to DESI, including the corrector barrel, hexapod and cage. The corrector barrel – designed, built and initially tested at Fermilab – aligns DESI’s six large lenses to within the accuracy of the width of a human hair. This precision is essential to ensure that the images DESI collects are sharp and clear. The hexapod, designed and built with partners in Italy, moves and focuses the lenses. Both the barrel and hexapod are housed in the cage, which was also designed and built by Fermilab. Additionally, Fermilab carried out the testing and packaging of the charge-coupled devices, or CCDs. The CCDs convert the light passing through these lenses from distant galaxies into digital information that can then be analyzed by the collaboration.

Fermilab also provided other components to the project, including the online databases used for data acquisition and the software that will ensure that each of the 5,000 robotic positioners are precisely pointing to their celestial targets.

“DESI promises to be at the core of the next decade of cosmological discoveries,” said Liz Buckley-Geer, a Fermilab scientist and a member of the DESI collaboration. “It’s an amazing project to be a part of, and we’re celebrating this moment with the entire DESI team.”

Members of the Fermilab team stand with the lens-holding barrel for the Dark Energy Spectroscopic Instrument. From left: Jorge Montes, Mike Roman, David Butler, Gaston Gutierrez, Giuseppe Gallo and Otto Alvarez. Photo: Reidar Hahn

On April 1 the dome of the Mayall Telescope near Tucson, Arizona, opened to the night sky, and starlight poured through the assembly of six large lenses that were carefully packaged and aligned for a new instrument that will launch later this year.

Just hours later, scientists produced the first focused images with these precision lenses – the largest is 1.1 meters in diameter – during this early test spin, marking an important “first light” milestone for the Dark Energy Spectroscopic Instrument, or DESI. This first batch of images homed in on the Whirlpool Galaxy to demonstrate the quality of the new lenses.

”It was an incredible moment to see those first images on the control room monitors,” said Connie Rockosi, who is leading this early commissioning of the DESI lenses. “A whole lot of people have worked really hard on this, and it’s really exciting to show how much has come together already.”

This phase of the project will continue for about six weeks and will require the efforts of several onsite scientists and remote observers, noted Rockosi, a professor of astronomy and astrophysics at UC Santa Cruz.

When completed later this year, DESI will see and measure the sky’s light in a far different way than this assembly of lenses. It is designed to take in thousands of points of light instead of a single, large picture.

The finished DESI will measure the light of tens of millions of galaxies reaching back 12 billion light-years across the universe. It is expected to provide the most precise measurement of the expansion of the universe and provide new insight into dark energy, which scientists explain is causing this expansion to accelerate.

DESI’s array of 5,000 independently swiveling robotic positioners, each carrying a thin fiber-optic cable, will automatically move into preset positions with accuracy to within several microns (millionths of a meter). Each positioner is programmed to point its fiber-optic cable at an object to gather its light.

That light will be channeled through the cables to a series of 10 devices known as spectrographs that will separate the light into thousands of colors. The light measurements, known as spectra, will provide detailed information about objects’ distance and the rate at which they are moving away from us, providing fresh insight about dark energy.

DESI’s lenses are housed in a barrel-shaped device known as a corrector that is attached above the telescope’s primary mirror, and the corrector is moved and focused by a surrounding device known as a hexapod.

Fermi National Accelerator Laboratory (Fermilab) researchers led the design, construction and initial testing of the corrector barrel, hexapod and supporting structures that hold the lenses in alignment.

“Our entire team is pleased to see this instrument achieve first light,” said Gaston Gutierrez, the Fermilab scientist who managed this part of the project. “It was a great challenge building such large devices to within the precision of a hair. We’re happy to see these systems come together.”

The giant corrector barrel and hexapod, which together weigh about 5 tons, must maintain alignment with the telescope’s large reflector mirror that is 12 meters below, all while compensating for the movement of the telescope’s assemblage of massive components as it swings across the sky.

“This is a big step up. It’s a leap into the future for the Mayall Telescope that will enable exciting new scientific discoveries,” said Michael Levi, DESI’s director and a physicist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), which is the lead institution in the international DESI collaboration. “The team has been working on the new corrector for the past five years, so it was quite an experience seeing $10 million of optics lifted by the crane during installation.”

The new set of lenses expands the telescope’s viewing window by about 16 times, enabling DESI to map about one-third of the visible sky several times during its five-year mission.

Peter Doel, a professor at University College London, led the team that designed the new optical system. “We had a half-dozen vendors involved with making and polishing the glass. One mistake would have spoiled everything. It’s thrilling to know that they survived the journey and work so well.”

“This was kind of the moment of truth,” said David Schlegel, a DESI project scientist. “We have been biting our nails.”

DESI “first light” image of the Whirlpool Galaxy, also known as Messier 51. This image was obtained the first night of observing with the DESI Commissioning Instrument on the Mayall Telescope at the Kitt Peak National Observatory in Tucson, Arizona; an r-band filter was used to capture the red light from the galaxy. Image: DESI collaboration

David Sprayberry, the National Optical Astronomy Observatory (NOAO) site director at Kitt Peak, said, “We have an amazing, multitalented team to make sure that everything is working properly,” including engineers, astronomers and telescope operators working in shifts. NOAO operates the Mayall Telescope and its Kitt Peak National Observatory site.

He noted the challenge in updating the sturdy, decades-old telescope, which started up in 1973, with high-precision equipment. “Ultimately we must make sure DESI can target to within 5-micron accuracy – not much larger than a human hair,” he said. That’s a big thing for something so heavy and big.” The entire moving weight of the Mayall Telescope is 375 tons.

Rockosi said there was intensive pre-planning for the corrector’s early testing, and many of the tasks during this testing stage are focused on gathering data from evening observations. While DESI scientists have created automated controls to help position, focus and align all of the equipment, this testing run allows the team to fine-tune these automated tools.

“We’ll look at bright stars and test how well we can keep the telescope targeted in the same place and measure image quality,” Rockosi said. “We will test that we can repeatedly and reliably keep those lenses in the best possible alignment.”

The precision testing of the corrector is made possible by an instrument – now mounted atop the telescope – that was designed and built by Ohio State University researchers. This 1-ton device, which features five digital cameras and measuring tools supplied by Yale University, and electronics supplied by the University of Michigan, is known as the commissioning instrument.

This temporary instrument was built at the same weight and installed at the same spot where DESI’s focal plane will be installed once it is fully assembled. The focal plane will carry DESI’s robotic positioners. The commissioning instrument simulates how the telescope will perform when carrying the full complement of DESI components and is verifying the quality of DESI’s lenses.

“One of the biggest challenges with the commissioning instrument was aligning all five cameras with the corrector’s curved focal surface,” said Paul Martini, an astronomy professor at Ohio State University who led the R&D and installation of the commissioning instrument and is now overseeing its use. “Another was measuring their positions to a few millionths of a meter, which is far more precise than most astronomical instruments.” This positioning will ensure truer measurements of the lenses’ performance.

He said he is looking forward to the installation of DESI’s focal plane later this year. That will pave the way for DESI’s official “first light” of its robotic positioners and the start of its galaxy measurements.

“What got me excited about this field in the first place was going to telescopes and taking data, so it will be fun to have this next step,” he said.

###

DESI is supported by the U.S. Department of Energy’s Office of Science; the U.S. National Science Foundation, Division of Astronomical Sciences under contract to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico; the Ministry of Economy of Spain; and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation. View the full list of DESI collaborating institutions, and learn more about DESI here: desi.lbl.gov.

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams,Lawrence Berkeley National Laboratoryand its scientists have been recognized with 13 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy’s Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

The National Optical Astronomy Observatory (NOAO)is the national center for ground-based nighttime astronomy in the United States and is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation Division of Astronomical Sciences.

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

The Heising-Simons Foundation is a family foundation based in Los Altos, California. The Foundation works with its many partners to advance sustainable solutions in climate and clean energy, enable groundbreaking research in science, enhance the education of our youngest learners, and support human rights for all people.

The Gordon and Betty Moore Foundation, established in 2000, seeks to advance environmental conservation, patient care and scientific research. The Foundation’s Science Program aims to make a significant impact on the development of provocative, transformative scientific research, and increase knowledge in emerging fields.

The Science and Technology Facilities Council (STFC) of the United Kingdom coordinates research on some of the most significant challenges facing society, such as future energy needs, monitoring and understanding climate change, and global security. It offers grants and support in particle physics, astronomy and nuclear physics; visit www.stfc.ac.uk.

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Barry Barish

On Wednesday, Feb. 13, Nobel laureate will present at the Fermilab Colloquium with a talk titled “Probing the Universe with Gravitational Waves.” The talk takes place at 4 p.m. in One West.

The discovery of gravitational waves, predicted by Einstein in 1916, is now enabling important tests of the theory of general relativity, as well as beginning multimessenger astronomy: the combined observations of astrophysical phenomena using electromagnetic radiation, gravitational waves and neutrinos.

Barish will explore plans and prospects for gravitational-wave science.

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The South Pole Telescope makes images of the cosmic microwave background to study the Big Bang at the beginning of the universe. Photo: Jason Gallicchio, University of Chicago

Chicago in January may feel like the coldest place in the universe, but it’s colder at the South Pole. Scientists there, including some from Fermilab, are looking out into space and observing microwaves that have been traveling at the speed of light for 13.6 billion years. Once they were ultraviolet rays, but as the universe expanded, their wavelengths stretched, and they became blue, then red, then infrared (heat) and now they are microwaves, which you may have in an oven in your kitchen. Radio waves have even longer wavelengths.

Just after the Big Bang at the beginning of our universe – I say “our” because ours may be one of many, we don’t yet know – everything was inconceivably hot. It cooled as it expanded, and now “space” is at about 2.7 Kelvin above absolute zero temperature. (Zero Kelvin is minus 460 degrees Fahrenheit, or minus 273 degrees Celsius.)

The universe is full of hot stars, and planets may be hot, warm or cold, but a rock in the depths of space would be bathed in microwaves at 2.7 K and be that cold. Nothing natural in the universe can be colder.

At absolute zero temperature, all atoms would stop jiggling and be still. According to quantum physics, that is not possible, and nothing can get as cold as absolute zero. In physics laboratories scientists have reached a millionth of a degree above absolute zero, but we can never quite get there.

The scientists at the South Pole use a microwave telescope to make maps of this “cosmic microwave background” to learn about the Big Bang. They are in Antarctica because the atmosphere there is transparent to microwaves, being thin, cold and dry, since water vapor freezes out. Also, they are far from civilization’s annoying background radiation. Thousands of tiny thermometers in this telescope are kept even colder, as they are extremely sensitive at only 0.4 K, at what is called a “superconducting phase transition.”

We think only a complicated physical apparatus can make anything colder than that 2.7 K bath, and scientists have reached that temperature only in the last 110 years. For how many centuries will science continue to be done? While there may be life on millions of planets, how many have active scientists? Only one? We could be unique.

So, if there are no other scientifically advanced civilizations in the Milky Way galaxy, there is no place as cold as in our laboratories. Not even Chicago in January.

This is a version of an article that appeared in Positively Naperville.

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Scientists’ effort to map a portion of the sky in unprecedented detail is coming to an end, but their work to learn more about the expansion of the universe has just begun.

The Dark Energy Camera is mounted on the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The final day of data-taking for the Dark Energy Survey is Jan. 9. Photo: Fermilab

After scanning in depth about a quarter of the southern skies for six years and cataloguing hundreds of millions of distant galaxies, the Dark Energy Survey (DES) will finish taking data tomorrow, on Jan. 9.

The survey is an international collaboration that began mapping a 5,000-square-degree area of the sky on Aug. 31, 2013, in a quest to understand the nature of dark energy, the mysterious force that is accelerating the expansion of the universe. Using the Dark Energy Camera, a 520-megapixel digital camera funded by the U.S. Department of Energy Office of Science and mounted on the Blanco 4-meter telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile, scientists on DES took data on 758 nights over six years.

Over those nights, they recorded data from more than 300 million distant galaxies. More than 400 scientists from over 25 institutions around the world have been involved in the project, which is hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory. The collaboration has already produced about 200 academic papers, with more to come.

According to DES Director Rich Kron, a Fermilab and University of Chicago scientist, those results and the scientists who made them possible are where much of the real accomplishment of DES lies.

“First generations of students and postdoctoral researchers on DES are now becoming faculty at research institutions and are involved in upcoming sky surveys,” Kron said. “The number of publications and people involved are a true testament to this experiment. Helping to launch so many careers has always been part of the plan, and it’s been very successful.”

The National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile houses the Dark Energy Camera. Photo: Fermilab

DES remains one of the most sensitive and comprehensive surveys of distant galaxies ever performed. The Dark Energy Camera is capable of seeing light from galaxies billions of light-years away and capturing it in unprecedented quality.

According to Alistair Walker of the National Optical Astronomy Observatory, a DES team member and the DECam instrument scientist, equipping the telescope with the Dark Energy Camera transformed it into a state-of-the-art survey machine.

“DECam was needed to carry out DES, but it also created a new tool for discovery, from the solar system to the distant universe,” Walker said. “For example, 12 new moons of Jupiter were recently discovered with DECam, and the detection of distant star-forming galaxies in the early universe, when the universe was only a few percent of its present age, has yielded new insights into the end of the cosmic dark ages.”

The survey generated 50 terabytes (that’s 50 million megabytes) of data over its six observation seasons. That data is stored and analyzed at the National Center for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign.

“Even after observations are ended, NCSA will continue to support the scientific productivity of the collaboration by making refined data releases and serving the data well into the 2020s,” said Don Petravick, senior project manager for the Dark Energy Survey at NCSA.

Now the job of analyzing that data takes center stage. DES has already released a full range of papers based on its first year of data, and scientists are now diving into the rich seam of catalogued images from the first several years of data, looking for clues to the nature of dark energy.

The first step in that process, according to Fermilab and University of Chicago scientist Josh Frieman, former director of DES, is to find the signal in all the noise.

“We’re trying to tease out the signal of dark energy against a background of all sorts of noncosmological stuff that gets imprinted on the data,” Frieman said. “It’s a massive ongoing effort from many different people around the world.”

The DES collaboration continues to release scientific results from their storehouse of data, and scientists will discuss recent results at a special session at the American Astronomical Society winter meeting in Seattle today, Jan. 8. Highlights from the previous years include:

DES scientists also spotted the first visible counterpart of gravitational waves ever detected, a collision of two neutron stars that occurred 130 million years ago. DES was one of several sky surveys that detected this gravitational wave source, opening the door to a new kind of astronomy.

Recently DES issued its first cosmology results based on supernovae (207 of them taken from the first three years of DES data) using a method that provided the first evidence for cosmic acceleration 20 years ago. More comprehensive results on dark energy are expected within the next few years.

The task of amassing such a comprehensive survey was no small feat. Over the course of the survey, hundreds of scientists were called on to work the camera in nightly shifts supported by the staff of the observatory. To organize that effort, DES adopted some of the principles of high-energy physics experiments, in which everyone working on the experiment is involved in its operation in some way.

“This mode of operation also afforded DES an educational opportunity,” said Fermilab scientist Tom Diehl, who managed the DES operations. “Senior DES scientists were paired with inexperienced ones for training and, in time, would pass that knowledge on to more junior observers.”

The organizational structure of DES was also designed to give early-career scientists valuable opportunities for advancement, from workshops on writing research proposals to mentors who helped review and edit grant and job applications.

Antonella Palmese, a postdoctoral researcher associate at Fermilab, arrived at Cerro Tololo as a graduate student from University College London in 2015. She quickly came up to speed and returned in 2017 and 2018 as an experienced observer. She also served as a representative for early-career scientists, helping to assist those first making their mark with DES.

“Working with DES has put me in contact with many remarkable scientists from all over the world,” Palmese said. “It’s a special collaboration because you always feel like you are a necessary part of the experiment. There is always something useful you can do for the collaboration and for your own research.”

The Dark Energy Camera will remain mounted on the Blanco telescope at Cerro Tololo for another five to 10 years and will continue to be a useful instrument for scientific collaborations around the world. Cerro Tololo Inter-American Observatory Director Steve Heathcote foresees a bright future for DECam.

“Although the data-taking for DES is coming to an end, DECam will continue its exploration of the universe from the Blanco telescope and is expected remain a front-line ‘engine of discovery’ for many years,” Heathcote said.

The DES collaboration will now focus on generating new results from its six years of data, including new insights into dark energy. With one era at an end, the next era of the Dark Energy Survey is just beginning.

Follow the Dark Energy Survey online at www.darkenergysurvey.org and connect with the survey on Facebook at www.facebook.com/darkenergysurvey, on Twitter at www.twitter.com/theDESurvey and on Instagram at www.instagram.com/darkenergysurvey.

The Dark Energy Survey is a collaboration of more than 400 scientists from 26 institutions in seven countries. Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, U.S. National Science Foundation, Ministry of Science, Innovation and Universities of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, ETH Zurich for Switzerland, National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and AstroParticle Physics at Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia, Deutsche Forschungsgemeinschaft, and the collaborating institutions in the Dark Energy Survey, the list of which can be found at www.darkenergysurvey.org/collaboration.

Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. NSF is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

NCSA at the University of Illinois at Urbana-Champaign provides supercomputing and advanced digital resources for the nation’s science enterprise. At NCSA, University of Illinois faculty, staff, students and collaborators from around the globe use advanced digital resources to address research grand challenges for the benefit of science and society. NCSA has been advancing one third of the Fortune 50® for more than 30 years by bringing industry, researchers and students together to solve grand challenges at rapid speed and scale. For more information, please visit www.ncsa.illinois.edu.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association Inc. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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The Dark Energy Spectroscopic Instrument seeks to further our cosmic understanding by creating the largest 3-D map of galaxies to date. Below is a press release issued by Lawrence Berkeley National Laboratory announcing first light for the optical lenses of this extraordinary instrument. The U.S. Department of Energy’s Fermi National Accelerator Laboratory is a key player in the construction of this instrument, drawing on more than 25 years of experience with the Sloan Digital Sky Survey and the Dark Energy Survey.

Fermilab contributed key elements to DESI, including the corrector barrel, hexapod and cage. The corrector barrel – designed, built and initially tested at Fermilab – aligns DESI’s six large lenses to within the accuracy of the width of a human hair. This precision is essential to ensure that the images DESI collects are sharp and clear. The hexapod, designed and built with partners in Italy, moves and focuses the lenses. Both the barrel and hexapod are housed in the cage, which was also designed and built by Fermilab. Additionally, Fermilab carried out the testing and packaging of the charge-coupled devices, or CCDs. The CCDs convert the light passing through these lenses from distant galaxies into digital information that can then be analyzed by the collaboration.

Fermilab also provided other components to the project, including the online databases used for data acquisition and the software that will ensure that each of the 5,000 robotic positioners are precisely pointing to their celestial targets.

“DESI promises to be at the core of the next decade of cosmological discoveries,” said Liz Buckley-Geer, a Fermilab scientist and a member of the DESI collaboration. “It’s an amazing project to be a part of, and we’re celebrating this moment with the entire DESI team.”

Members of the Fermilab team stand with the lens-holding barrel for the Dark Energy Spectroscopic Instrument. From left: Jorge Montes, Mike Roman, David Butler, Gaston Gutierrez, Giuseppe Gallo and Otto Alvarez. Photo: Reidar Hahn

On April 1 the dome of the Mayall Telescope near Tucson, Arizona, opened to the night sky, and starlight poured through the assembly of six large lenses that were carefully packaged and aligned for a new instrument that will launch later this year.

Just hours later, scientists produced the first focused images with these precision lenses – the largest is 1.1 meters in diameter – during this early test spin, marking an important “first light” milestone for the Dark Energy Spectroscopic Instrument, or DESI. This first batch of images homed in on the Whirlpool Galaxy to demonstrate the quality of the new lenses.

”It was an incredible moment to see those first images on the control room monitors,” said Connie Rockosi, who is leading this early commissioning of the DESI lenses. “A whole lot of people have worked really hard on this, and it’s really exciting to show how much has come together already.”

This phase of the project will continue for about six weeks and will require the efforts of several onsite scientists and remote observers, noted Rockosi, a professor of astronomy and astrophysics at UC Santa Cruz.

When completed later this year, DESI will see and measure the sky’s light in a far different way than this assembly of lenses. It is designed to take in thousands of points of light instead of a single, large picture.

The finished DESI will measure the light of tens of millions of galaxies reaching back 12 billion light-years across the universe. It is expected to provide the most precise measurement of the expansion of the universe and provide new insight into dark energy, which scientists explain is causing this expansion to accelerate.

DESI’s array of 5,000 independently swiveling robotic positioners, each carrying a thin fiber-optic cable, will automatically move into preset positions with accuracy to within several microns (millionths of a meter). Each positioner is programmed to point its fiber-optic cable at an object to gather its light.

That light will be channeled through the cables to a series of 10 devices known as spectrographs that will separate the light into thousands of colors. The light measurements, known as spectra, will provide detailed information about objects’ distance and the rate at which they are moving away from us, providing fresh insight about dark energy.

DESI’s lenses are housed in a barrel-shaped device known as a corrector that is attached above the telescope’s primary mirror, and the corrector is moved and focused by a surrounding device known as a hexapod.

Fermi National Accelerator Laboratory (Fermilab) researchers led the design, construction and initial testing of the corrector barrel, hexapod and supporting structures that hold the lenses in alignment.

“Our entire team is pleased to see this instrument achieve first light,” said Gaston Gutierrez, the Fermilab scientist who managed this part of the project. “It was a great challenge building such large devices to within the precision of a hair. We’re happy to see these systems come together.”

The giant corrector barrel and hexapod, which together weigh about 5 tons, must maintain alignment with the telescope’s large reflector mirror that is 12 meters below, all while compensating for the movement of the telescope’s assemblage of massive components as it swings across the sky.

“This is a big step up. It’s a leap into the future for the Mayall Telescope that will enable exciting new scientific discoveries,” said Michael Levi, DESI’s director and a physicist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), which is the lead institution in the international DESI collaboration. “The team has been working on the new corrector for the past five years, so it was quite an experience seeing $10 million of optics lifted by the crane during installation.”

The new set of lenses expands the telescope’s viewing window by about 16 times, enabling DESI to map about one-third of the visible sky several times during its five-year mission.

Peter Doel, a professor at University College London, led the team that designed the new optical system. “We had a half-dozen vendors involved with making and polishing the glass. One mistake would have spoiled everything. It’s thrilling to know that they survived the journey and work so well.”

“This was kind of the moment of truth,” said David Schlegel, a DESI project scientist. “We have been biting our nails.”

DESI “first light” image of the Whirlpool Galaxy, also known as Messier 51. This image was obtained the first night of observing with the DESI Commissioning Instrument on the Mayall Telescope at the Kitt Peak National Observatory in Tucson, Arizona; an r-band filter was used to capture the red light from the galaxy. Image: DESI collaboration

David Sprayberry, the National Optical Astronomy Observatory (NOAO) site director at Kitt Peak, said, “We have an amazing, multitalented team to make sure that everything is working properly,” including engineers, astronomers and telescope operators working in shifts. NOAO operates the Mayall Telescope and its Kitt Peak National Observatory site.

He noted the challenge in updating the sturdy, decades-old telescope, which started up in 1973, with high-precision equipment. “Ultimately we must make sure DESI can target to within 5-micron accuracy – not much larger than a human hair,” he said. That’s a big thing for something so heavy and big.” The entire moving weight of the Mayall Telescope is 375 tons.

Rockosi said there was intensive pre-planning for the corrector’s early testing, and many of the tasks during this testing stage are focused on gathering data from evening observations. While DESI scientists have created automated controls to help position, focus and align all of the equipment, this testing run allows the team to fine-tune these automated tools.

“We’ll look at bright stars and test how well we can keep the telescope targeted in the same place and measure image quality,” Rockosi said. “We will test that we can repeatedly and reliably keep those lenses in the best possible alignment.”

The precision testing of the corrector is made possible by an instrument – now mounted atop the telescope – that was designed and built by Ohio State University researchers. This 1-ton device, which features five digital cameras and measuring tools supplied by Yale University, and electronics supplied by the University of Michigan, is known as the commissioning instrument.

This temporary instrument was built at the same weight and installed at the same spot where DESI’s focal plane will be installed once it is fully assembled. The focal plane will carry DESI’s robotic positioners. The commissioning instrument simulates how the telescope will perform when carrying the full complement of DESI components and is verifying the quality of DESI’s lenses.

“One of the biggest challenges with the commissioning instrument was aligning all five cameras with the corrector’s curved focal surface,” said Paul Martini, an astronomy professor at Ohio State University who led the R&D and installation of the commissioning instrument and is now overseeing its use. “Another was measuring their positions to a few millionths of a meter, which is far more precise than most astronomical instruments.” This positioning will ensure truer measurements of the lenses’ performance.

He said he is looking forward to the installation of DESI’s focal plane later this year. That will pave the way for DESI’s official “first light” of its robotic positioners and the start of its galaxy measurements.

“What got me excited about this field in the first place was going to telescopes and taking data, so it will be fun to have this next step,” he said.

###

DESI is supported by the U.S. Department of Energy’s Office of Science; the U.S. National Science Foundation, Division of Astronomical Sciences under contract to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico; the Ministry of Economy of Spain; and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation. View the full list of DESI collaborating institutions, and learn more about DESI here: desi.lbl.gov.

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams,Lawrence Berkeley National Laboratoryand its scientists have been recognized with 13 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department of Energy’s Office of Science.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

The National Optical Astronomy Observatory (NOAO)is the national center for ground-based nighttime astronomy in the United States and is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation Division of Astronomical Sciences.

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

The Heising-Simons Foundation is a family foundation based in Los Altos, California. The Foundation works with its many partners to advance sustainable solutions in climate and clean energy, enable groundbreaking research in science, enhance the education of our youngest learners, and support human rights for all people.

The Gordon and Betty Moore Foundation, established in 2000, seeks to advance environmental conservation, patient care and scientific research. The Foundation’s Science Program aims to make a significant impact on the development of provocative, transformative scientific research, and increase knowledge in emerging fields.

The Science and Technology Facilities Council (STFC) of the United Kingdom coordinates research on some of the most significant challenges facing society, such as future energy needs, monitoring and understanding climate change, and global security. It offers grants and support in particle physics, astronomy and nuclear physics; visit www.stfc.ac.uk.

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For The New York Times, Feb. 25, 2019: Axions? Phantom energy? Astrophysicists scramble to patch a hole in the universe, rewriting cosmic history in the process. Fermilab scientist Josh Frieman is quoted in this article.
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Barry Barish

On Wednesday, Feb. 13, Nobel laureate will present at the Fermilab Colloquium with a talk titled “Probing the Universe with Gravitational Waves.” The talk takes place at 4 p.m. in One West.

The discovery of gravitational waves, predicted by Einstein in 1916, is now enabling important tests of the theory of general relativity, as well as beginning multimessenger astronomy: the combined observations of astrophysical phenomena using electromagnetic radiation, gravitational waves and neutrinos.

Barish will explore plans and prospects for gravitational-wave science.

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