In search of mapping the universe, astrophysicists launch largest study of the sky ever

The Dark Energy Spectroscopic Instrument (DESI) installed on the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, AZ. Credit: KPNO / NOIRLab / NSF / AURA / P. Marenfeld

Almost 40 years after creating the first iconic map of the universe, researchers are aiming for the largest map ever created.

In 1983, the astrophysicists of the Center d’Astrophysique | Harvard and Smithsonian (CfA) published a cosmic map using 2,400 galaxies. Now, CFA scientists aim to map 30 million.

In the largest quest to date to map the universe, an international team of researchers are using DESI, or the dark energy spectroscopic instrument, to probe the sky. Sightings officially began today, May 17, at the Kitt Peak National Observatory near Tucson, Arizona; the mission will last five years with the objective of mapping 30 million galaxies.

By surveying a vast volume of space, scientists in the DESI collaboration – including a dozen from the CfA – will be able to answer a myriad of questions from modern cosmology: how does the early universe create large-scale structures, how does gravity cause matter to collect and form galaxies, and what could be behind the enigmatic acceleration of the universe’s expansion?

The first maps of the universe

Mapping the universe has a long history at CfA, explains Douglas Finkbeiner, researcher at CfA and member of the DESI collaboration.

Pioneering CfA astrophysicists launched the first systematic surveys to map the universe in the late 1970s. Led by Marc Davis, John Huchra, Dave Latham and John Tonry, the team initially targeted 2,400 galaxies, measuring their redshifts – the offset of the wavelength of light from an object in space – which can be used to calculate distance from Earth.

The second, more extensive map of Margaret Geller and Huchra, revealed on the blanket of Science in November 1989, was revolutionary. He revealed the cosmic web for the first time, showing that galaxies are not evenly distributed in space, but rather are divided into clusters with large regions of empty space between them.

It was around this time that CfA astrophysicist Margaret Geller coined the term “soap bubble universe”When, after creating the first maps, they realized that these galaxy clusters were sitting on the membranes of what appeared to be large, invisible bubbles that stretched millions of light years.

Dark Energy Spectroscopic Instrument Mayall Telescope

The Dark Energy Spectroscopic Instrument (DESI) is mounted on the 4m Mayall Telescope at Kitt Peak National Observatory. Credit: P. Marenfeld & NOAO / AURA / NSF

The road to follow

But what cosmic forces create and shape these bubbles? Scientists are now deducing the action of two invisible actors – dark matter and dark energy – whose physical origins remain mysterious, thus requiring other observational clues to understand their nature and composition.

This is where DESI can help.

Built by a collaboration of hundreds of people and with principal funding from the US Department of Energy Office of Science, DESI was installed and is now operating on the modernized Nicholas U. Mayall 4-meter telescope at Kitt National Observatory Peak. The instrument will allow scientists to study redshifts on an unprecedented scale. Using 5,000 robot-controlled optical fibers, DESI can collect spectroscopic, or light, data from 5,000 galaxies at a time.

By collecting light from over 30 million galaxies, DESI will help build a detailed 3D map of the universe that dates back 11 billion years. The map will help better understand the repulsive force associated with dark energy that has caused the universe to expand exponentially for billions of years.

“DESI is a finely tuned machine, leveraging the opportunities of the latest technology and drawing on decades of experience in optimizing the hardware, software and operational strategy of large sky surveys,” says Daniel Eisenstein, researcher at CfA and member of DESI. collaboration. “The result is quite astonishing: an installation around 20 times faster than the previous advanced technology. We are acquiring redshifts of galaxies 100 times lower than what we targeted with the Sloan Digital Sky Survey just 20 years ago. “

As DESI data begins to arrive, Eisenstein and the CfA team will see how it compares to current theories of cosmological structure. He and his colleagues used America’s fastest supercomputer, Summit at Oak Ridge National Laboratory, to create simulations of the formation of the large-scale galaxy cluster and the role dark energy played in it. .

Finkbeiner, who helped decide which targets DESI would observe over the next five years, believes there’s still a lot to learn from redshift’s investigations.

“Redshift surveys provide key information about how much matter is in the universe and how it aggregates,” he says. “We can now measure so many galaxies with such precision that they also give us a sense of dark energy and neutrinos. Today we celebrate the start of the DESI survey and look forward to the new findings it will bring. “

About Dianne Stinson

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