Free Astronomy Magazine July-August 2026

44 JULY-AUGUST 2026 ASTRO PUBLISHING chine with thousands of parts to maintain. In 2020, final tests of the instru- ment were interrupted by the COVID-19 pandemic. In 2022, the Contreras Fire swept over Kitt Peak but, through the efforts of fire- fighters and staff, did not damage the telescope. Re- covery efforts were slowed by monsoons and mud- slides. DESI will continue observa- tions through 2028 and grow its map by about 20%, from 14,000 square degrees to 17,000 square degrees. (For comparison, the Moon covers approxi- mately 0.2 square degrees, and the full sky has over 41,000 square degrees). The extended map will cover parts of the sky that are more challenging to observe: areas that are closer to the plane of the Milky Way, where bright nearby stars can make it harder to see more distant objects, or further to the south, where the telescope must ac- count for peering through more of Earth’s atmosphere. The experiment will also revisit the existing area of the map to collect data from a new set of galaxies: more distant, fainter “luminous red galaxies.” These will provide an even denser, more detailed map of the regions DESI has already cov- ered, giving researchers a clearer picture of the Universe’s history. Researchers will also study nearby dwarf galaxies and stellar streams, bands of stars torn from smaller galaxies by the Milky Way’s gravity. The hope is to better understand dark matter, the invisible form of matter that accounts for most of the mass in the Universe but has never been directly detected. A thin slice of the map produced by the DESI five-year survey shows galaxies and quasars above and below the plane of the Milky Way. The Universe’s large-scale structure is visible in the magnified inset. Earth lies at the center of the wedges, and the black gap marks where our own galaxy obscures distant objects. Light from the furthest galaxies shown is 11 billion years old by the time it reaches Earth. [Claire Lamman/DESI collaboration] ready seeing and the discoveries yet to come as we continue to explore the mysteries of our cosmos.” “DESI’s five-year survey has been spectacularly successful,” says Mi- chael Levi, DESI director and a scien- tist at Berkeley Lab. “The instru- ment performed better than antici- pated. The results have been incred- ibly exciting. And the size and scope of the map, and how quickly we’ve been able to execute, is phenome- nal. We’re going to celebrate com- pletion of the original survey and then get started on the work of churning through the data, because we’re all curious about what new surprises are waiting for us.” DESI has now measured cosmologi- cal data for six times as many gal- axies and quasars as all previous measurements combined. The col- laboration will immediately begin processing the completed dataset, with the first dark energy results from the full five-year survey ex- pected in 2027. In the meantime, DESI collaborators continue to ana- lyze the survey’s first three years of data, refining dark energy measure- ments and producing additional re- sults on the structure and evolution of the Universe, with several papers planned later this year. DESI began collecting data in May 2021. Since then, the instrument has far surpassed the collaboration’s original goals. The plan was to cap- ture light from 34 million galaxies and quasars (extremely distant yet bright objects with black holes at their cores) over the five-year sky survey. DESI instead observed more than 47 million galaxies and qua- sars, as well as 20 million stars. The project’s success is even more impressive in light of several chal- lenges. DESI is a complicated ma- !