SDSS-V

SDSS-V. The fifth generation of the Sloan Digital Sky Survey, it is an ambitious, all-sky spectroscopic survey designed to create a dynamic, three-dimensional map of the Milky Way, the Local Group, and the distant universe. Building upon the monumental legacy of its predecessors, this project represents a paradigm shift towards time-domain and multi-object spectroscopy on an unprecedented scale. Officially commencing operations in 2020, it leverages innovative robotic technology at observatories in both the northern and southern hemispheres to collect vast amounts of astrophysical data.

Overview

SDSS-V is directed by the international Sloan Digital Sky Survey collaboration, with major participating institutions including the Max Planck Institute for Astronomy and numerous universities worldwide. The project operates from two primary sites: the existing facility at Apache Point Observatory in New Mexico and a new southern station at Las Campanas Observatory in Chile, home to the Magellan Telescopes. This dual-hemisphere approach is fundamental to achieving its goal of all-sky coverage. The survey officially entered its operational phase after the conclusion of SDSS-IV, with first light for its new instruments achieved in the latter half of 2020. The project is structured as a three-pillar survey, with each component targeting specific, transformative scientific questions across cosmic time and distance scales.

Scientific goals

The core mission is articulated through three interconnected, large-scale programs. The first, the Milky Way Mapper, aims to unravel the full formation history and evolution of our Galaxy by obtaining spectra for millions of stars, probing kinematics, chemistry, and stellar ages. The second pillar, the Black Hole Mapper, seeks to understand the growth of supermassive black holes and the physics of accretion by repeatedly observing hundreds of thousands of quasars and the nuclei of active galaxies like NGC 4151. The final component, the Local Volume Mapper, will conduct integral field unit spectroscopy to study the interstellar medium, star formation, and feedback processes in nearby galaxies and nebulae such as the Orion Nebula, providing a detailed view of galactic ecosystems.

Survey components

The Milky Way Mapper component will target over six million stars across the Galactic disk, Galactic halo, and nearby stellar streams, building upon the work of missions like Gaia (spacecraft) and TESS (spacecraft). The Black Hole Mapper is designed as a multi-epoch survey, monitoring the variability of accretion disks around black holes across cosmic time, from the nearby universe to the epoch of reionization. The Local Volume Mapper will utilize a network of fiber bundles to obtain spatially resolved spectra for thousands of objects in the local universe, creating detailed maps of physical conditions in regions like the Triangulum Galaxy and the Large Magellanic Cloud. Together, these programs ensure spectroscopic data is collected for targets ranging from nearby brown dwarfs to the most distant quasars.

Technology and instrumentation

A key technological innovation is the use of robotic fiber positioners. Hundreds of these small robots, installed at the focal planes of the Apache Point Observatory 2.5-meter telescope and the Las Campanas Observatory 2.5-meter Irénée du Pont Telescope, can rapidly reconfigure optical fibers to precisely align with pre-selected celestial targets. This system allows for highly efficient observation of thousands of objects simultaneously. The survey employs a suite of spectrographs, including upgraded versions of the BOSS spectrograph and new, high-resolution instruments, capable of observing from the ultraviolet to the near-infrared. This robotic multi-object spectroscopy system represents a significant advance over the manually plugged plates used in earlier SDSS generations.

Data releases and legacy

Following the open-access policy established by SDSS-I, all data will be made publicly available through regular data releases via the NASA Astrophysics Data System and the survey's own portal. The final legacy dataset will include spectra, derived physical parameters, and catalogs that will serve as fundamental resources for astronomers for decades. These data will complement and enhance findings from other major facilities like the Hubble Space Telescope, the James Webb Space Telescope, and the upcoming Vera C. Rubin Observatory. By charting the galactic archaeology of the Milky Way, the growth cycles of black holes, and the complexity of nearby galaxies, SDSS-V is poised to provide foundational insights into the architecture and evolution of the cosmos.