Free Astronomy Magazine March-April 2023

19 T he Milky Way Galaxy contains hundreds of billions of stars, glimmering star-forming re- gions, and towering dark clouds of dust and gas. Imaging and cataloging these objects for study is a herculean task, but a newly released astronom- ical dataset known as the second data release of the Dark Energy Cam- era Plane Survey (DECaPS2) reveals a staggering number of these objects in unprecedented detail. The DECaPS2 survey, which took two years to complete and produced more than 10 terabytes of data from 21,400 individual exposures, identi- fied approximately 3.32 billion ob- jects — arguably the largest such catalog compiled to date. As- tronomers and the public can explore the dataset here https://decaps.lega- cysurvey.org/viewer. This unprecedented collection was captured by the Dark Energy Cam- era (DECam) instrument on the Víc- tor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Obser- vatory (CTIO), a Program of NSF’s NOIRLab. CTIO is a constellation of international astronomical tele- scopes perched atop Cerro Tololo in Chile at an altitude of 2200 meters (7200 feet). CTIO’s lofty vantage point gives astronomers an unri- valed view of the southern celestial hemisphere, which allowed DECam to capture the southern Galactic plane in such detail. DECaPS2 is a survey of the plane of the Milky Way as seen from the southern sky taken at optical and near-infrared wavelengths. The first A stronomers have released a gargantuan survey of the galactic plane of the Milky Way. The new dataset contains a staggering 3.32 billion ce- lestial objects — arguably the largest such catalog so far. The data for this unprecedented survey were taken with the US Department of Energy-fab- ricated Dark Energy Camera at the NSF’s Cerro Tololo Inter-American Ob- servatory in Chile, a Program of NOIRLab. For reference, a low-resolution image of the DECaPS2 data is overlaid on an image showing the full sky. The callout box is a full-resolution view of a small portion of the DECaPS2 data. [DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/ NSF/AURA/E. Slawik. Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)]