@energy

class="content__text" SEEING BACK IN TIME: You may think you’d need a time machine to look back in space 11 billion years ago – more than twice as long as the Earth’s lifetime. However, the Dark Energy Spectroscopic Instrument (DESI) is making it possible. Even though light is the fastest thing in the universe, it still has limits. If a star that is three million light years away explodes today, that light won’t get to Earth until three million years later. In addition, the universe is constantly expanding. As galaxies move further away from us, their light shifts to longer, redder wavelengths. The further away an object is, the “redder” its wavelength, which is called a redshift. By measuring the wavelengths of light coming from galaxies, we can understand how far away they are and look back in time. That’s where DESI comes in. DESI is an instrument mounted on the Mayall telescope in Arizona. A team with scientists from 13 nations collaborated on building the tool, led by DOE’s Lawrence Berkeley National Laboratory. (Several other national labs are partners as well.) It started taking data in May 2021 and will be running until 2026. DESI has 5,000 robotically controlled optical fibers. Each one of these fibers captures information on a single object in the telescope’s field of view. Whenever the telescope is pointing at a section of the sky, it is taking data on 5,000 galaxies simultaneously. Scientists can take snapshots of how the universe looked at different periods of time. They expect the tool to reach back as far as 11 billion years. This data can also give us information on a galaxy’s chemical composition and velocity. Eventually, it will capture information on light from 30 million galaxies. With this data, scientists are developing 3D maps of the universe. These maps provide insight into why the universe is expanding ever more quickly, a phenomenon scientists call “dark energy.” Photo description: Photo of DESI, which has a giant blue metal ring on a platform with scaffolding above it. The white tiled ceiling of the building arcs around it. Photo credit: Marilyn Chung/Lawrence Berkeley National Laboratory

May 06, 2023