![]() The faster the universe is expanding and the farther an object’s distance, the redder it appears. All of these measurements are based on cosmological redshift, the stretching of light toward longer (redder) wavelengths as the universe expands. The spectra reveal vital details about each galaxy: age, distance, and velocity. ![]() The fibers produce spectra of thousands of galaxies with each exposure, divided into red, blue, and near-infrared wavelengths. Inside DESI, six lenses focus light from the Mayall’s primary mirror onto optical fibers split into 10 bundles of 500 strands each, which lead to a sealed room one floor below. With a field of view 38 times larger than the Full Moon, it can obtain spectra of extremely faint galaxies up to 12 billion years old using 5,000 robotically positioned optical fibers. Since 2021, DESI has been collecting data from over 30 million distant galaxies to create a three-dimensional map of the universe, reconstructing how it has evolved since the Big Bang.ĭESI is one of the most powerful instruments of its kind in the world. The instrument was built with funding from the Department of Energy for a singular, five-year mission: to determine the role of dark energy in the universe’s ongoing expansion. That’s what KPNO and its owner, the National Science Foundation (NSF), did to the Mayall in 2018, when engineers replaced its secondary mirror with a state-of-the-art spectrograph called the Dark Energy Spectroscopic Instrument (DESI). You can take a telescope that is 40 years old and put in leading-edge instrumentation, and you basically are at the forefront of science.” “But the bang for the buck comes with the instrumentation that you put on a telescope. “It’s a behemoth,” says Kitt Peak’s associate director, Michelle Edwards, and, in some ways, a relic. The telescope has retained its original 15-ton, 4-meter solid glass primary mirror and equatorial mount. ![]() That concept was eventually abandoned for simpler, more compact designs, but the long elevator ride to the top-floor control room still inspires visions of astronomers peering skyward from precarious ladders. The Mayall and the 18-story-tall building that houses it date from a time when tall domes were considered crucial for still air and optimal observing. But when the smoke cleared, KPNO’s 18-story Mayall telescope dome was still standing, visible from Tucson 40 miles (64 kilometers) to the northeast and towering above almost two dozen smaller domes. In June, the entire KPNO complex narrowly escaped annihilation in the nearly 29,500-acre Contreras Fire. Last summer, I set out to explore the Triangle, determined to find out how these observatories were adapting to today’s challenges, including weathering the COVID-19 pandemic and the increasing threat of devastating forest fires. ![]()
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