The universe is extremely large and complex, so much so that the English language contains an adverb, ‘astronomically’, so that we can compare anything to the sheer scale of the cosmos. Given all of this, it may seem impossible to create an accurate three-dimensional map of the entire universe, one which pinpoints the locations of millions of galaxies and the structures that encompass them.

Yet that is exactly what the Dark Energy Spectroscopic Instrument (DESI) has been working on for the past seven months. The map is record-breaking in size, as it spans 11 billion light years and dwarfs every other map of the universe combined. 

DESI was created mainly to help scientists understand the accelerating expansion of the universe. The current understanding of the universe’s expansion is that a force called ‘dark energy’, which makes up about 70% of the universe, causes the expansion of the universe to accelerate, rather than slowing down due to gravity. However, there is no consensus on the properties of dark energy, or even what it is in the first place. Is it a fundamental property of space, or a sort of fluid that permeates the universe, or a consequence of a hitherto unknown theory of gravity? According to NASA, the best way to find the answer is “more data, better data.” 

Work on the project started in 2015, and it was installed at the Kitt Peak National Observatory in Tucson, Arizona. Progress was delayed briefly due to the COVID-19 pandemic, but by May 2021, the instrument was ready to start its survey. 

The instrument consists of 5000 optical fibers, each held by a pencil-sized robot. The robots control the position of the optical fibers with extreme accuracy – the positions of the fibers must be accurate to within ten microns, less than the width of a human hair.

The light then travels down the optical fibers to a separate room, where huge instruments called spectroscopes measure the wavelengths of light to determine how far away the galaxies are, and how quickly they are moving away from us (longer wavelengths represent galaxies that are moving away more quickly). 

With all of this data, scientists have constructed a 3D map of the universe that spans a third of the night sky. Inside the map, huge cosmic structures, superclusters made of galaxies and filaments made of superclusters, can be clearly seen.

This data can be used to trace the history of the universe’s expansion, which, in turn, can help us understand dark energy better. With that knowledge, scientists can predict how the universe will change in the future, including how it might end. 

In addition, the data can help with the study of galactic cores (specifically, the activity in the nuclei of smaller galaxies), dark matter (a mysterious type of matter that is difficult to detect but exerts a gravitational force), and quasars (extremely bright galaxies), all of which are crucial subjects in astronomy. 

Even though the instrument has made significant progress, it is actually only 10% of its way through its mission to map the universe. Once its five-year mission is over, scientists will be able to fully use the data to look into the ancient past of the universe.

Sources:

1. Becker, Adam. “Dark Energy Spectroscopic Instrument (DESI) Creates Largest 3D Map of the Cosmos -.” Berkeley Lab News Center, 13 January 2022, https://newscenter.lbl.gov/2022/01/13/dark-energy-spectroscopic-instrument-desi-creates-largest-3d-map-of-the-cosmos/. Accessed 24 January 2022.

2. Buongiorno, Caitlyn. “Charting the universe in 3D | Astronomy.com.” Astronomy Magazine, 21 January 2022, https://astronomy.com/news/2022/01/desi-charting-the-universe. Accessed 24 January 2022.

3. “Dark Energy, Dark Matter | Science Mission Directorate.” NASA Science, https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy. Accessed 24 January 2022.

4. Friesen, Josh. “Scientists create largest 3D map of the cosmos.” Ohio State News, 13 January 2022, https://news.osu.edu/scientists-create-largest-3d-map-of-the-cosmos/. Accessed 24 January 2022.

5. Nield, David. “Take a Look at The Largest And Most Detailed 3D Map of The Universe Ever Made.” ScienceAlert, 14 January 2022, https://www.sciencealert.com/we-now-have-the-largest-and-most-detailed-3d-map-of-the-universe-ever-made. Accessed 24 January 2022.

6. Pultarova, Tereza. “How 5000 Pencil-Size Robots May Solve the Mysteries of the Universe.” Live Science, 16 February 2018, https://www.livescience.com/61791-pencil-robots-may-solve-universe-mysteries.html. Accessed 24 January 2022.