The Sloan Digital Sky Survey has been working for more than 20 years to make maps of the Universe. The video below shows a flythrough of the SDSS’s map of the large-scale structure of the Universe created in the first two phases of the project. This animated flythrough shows what our view of the Universe has become thanks to the data of the Sloan Digital Sky Survey.
While this map is a major accomplishment in itself; the true success of SDSS is the revolutionary new knowledge that is gained as a result of these maps. SDSS-I through-V have produced a large number of publications in refereed journals, and will continue to add many more as the survey progresses and new data is obtained. To see the updated list of SDSS-V publications, please visit our Publications page.
To learn more about some of our biggest discoveries, see the list of Press Releases on our News page.
A Flight through the Universe
This animated flythrough shows what our view of the Universe has become thanks to the data of the Sloan Digital Sky Survey.
The Science of SDSS-V
SDSS-V is now pioneering panoptic spectroscopy: it is first sky survey to carry out all-sky, time-domain spectroscopy in both the optical and the infrared, and to push integral-field unit spectroscopy (IFS) towards the ultra-wide area regime. The astrophysical goals of SDSS-V range from stellar and ISM physics to the evolution of our Milky Way, and to the growth of supermassive black holes. See below for more details about many of the exciting topics SDSS-V will address.
Black Holes
Mapping Supermassive Black Holes
Quasars are among the most luminous objects in the Universe. Powered by accretion onto supermassive black holes (SMBHs), quasars (or Active Galactic Nuclei – AGN) are beacons marking and tracing the growth of SMBHs across cosmic distance and time. Black holes are mathematically simple objects, but they are astrophysically complex. Through its Black Hole Mapper program, SDSS-V will provide more than 10 times more black holes with masses from reverberation mapping, about 20,000 quasars with multi-epoch monitoring, and nearly half a million black holes with X-ray measurements, adding wide-area, multi-epoch optical spectroscopy to the era of time-domain imaging and the next-generation sky surveys (e.g., ZTF, LSST, and eROSITA).
Black Hole Mass and Reverberation Mapping
One of the most fundamental characteristics of a black hole – mathematically and astrophysically – is its mass. In SDSS-V we are making precise measurements of black hole masses and their growth through time-domain spectroscopy in our Black Hole Mapper program. Reverberation mapping (RM) of the broad-line region (BLR) remains one of the most direct techniques to measure supermassive black hole masses. By correlating time delays between continuum and emission line variability, RM estimates the characteristic size of the BLR. When combined with the velocity widths of broad emission lines, this yields a virial mass estimate—the most fundamental parameter for understanding black hole demographics. Yet existing RM samples are small and biased toward nearby, low-luminosity active galactic nuclei (AGN), with fewer than 100 well-characterized systems to date. SDSS-V will change that. By measuring RM lags and line widths for ~1,000 quasars spanning a wide range of luminosities and redshifts, SDSS-V will revolutionize our understanding of black hole growth across cosmic time.
Variability of Accreting Supermassive Black Holes
In addition to the reverberation mapping data (below), SDSS-V will definitively characterize the spectral variability of more than 20,000 other quasars, sampling light-travel, dynamical, and thermal timescales of days to decades; revealing emission line profile variations; SMBH binarity; and rare “changing-look” quasars that shut off/on in just a few years, challenging our fundamental assumptions of SMBH accretion astrophysics.
High Energy Black Hole Astrophysics
The SRG/eROSITA mission is transforming X-ray astronomy, discovering in its first 12 months as many sources as were catalogued in the prior five decades. Unlocking the astrophysics behind these sources requires detailed spectroscopic follow-up to identify object types and measure redshifts. SDSS-V will provide optical spectra for hundreds of thousands of eROSITA sources (to i<21.5), enabling classification of obscured and unobscured AGN, galaxy clusters, X-ray-bright stars, transients, and rare exotic objects. This massive effort will build the definitive bridge between X-ray discoveries and optical diagnostics, revealing how X-ray luminous populations trace cosmic structure and evolution.
The Baryon Cycle and the Making of the Milky Way
Star formation and feedback reshape the interstellar medium (ISM), drive the galaxy’s baryon cycle, and shape its billions-year-long history. SDSS-V will study these phenomena through two programs: the Local Volume Mapper, using LVM-i, our new Southern Hemisphere integral field unit (IFU); and the Milky Way Mapper, using the APOGEE and BOSS spectrographs.
Interstellar Gas Structures
SDSS-V’s Local Volume Mapper will map ionized gas emission across thousands of square degrees in the Galactic plane and Magellanic Clouds at spatial scales of 0.1–10 pc—resolving knots of star formation and complex shock networks. These maps will link gas dynamics from parsec to kiloparsec scales, bridging the physics of ISM structure, star formation, and feedback.
The Young Milky Way
Understanding the physics of star formation requires studying young stellar populations and their natal environments. SDSS-V’s Milky Way Mapper will spectroscopically classify and characterize ~100,000 young stars, spanning the full stellar mass range—from massive, short-lived O stars to faint, embedded M dwarfs. Meanwhile, the Local Volume Mapper will observe nearly every known star-forming region within 3 kpc and all optically visible regions in the Magellanic Clouds. These observations will capture how stars interact with their environments and shed light on the earliest phases of stellar and planetary system evolution. By observing gas and stars in diverse environments, SDSS-V will explore how Galactic-scale features like spiral arms regulate star formation, and how the physical properties of star-forming clouds influence the mass distribution and multiplicity of newborn stars.
Galactic Archaeology
To reconstruct the Milky Way’s formation and evolutionary history, we must map its stellar fossil record in detail. SDSS-V’s Milky Way Mapper will deliver the first contiguous, densely sampled spectroscopic map of the entire sky using near-infrared observations of millions of stars. Combined with Gaia , this high-dimensional dataset—spanning chemistry, kinematics, and age—will uncover the chemical and dynamical structure of the Galaxy across scales from 100 pc to 10 kpc. SDSS-V’s Galactic Genesis Survey (GGS) targets luminous red giants to probe where the Galaxy’s mass resides, including over 3 million stars to construct a high-resolution dust map of the Galactic plane. Together with Gaia and TESS , SDSS-V defines a new era of precision Galactic Archaeology.
The Physics of Stars
Stellar Astrophysics and Asteroseismology
Galactic and extragalactic evolution models hinge on a deep understanding of stellar life cycles. Seismic data from TESS, combined with SDSS-V spectroscopy, will tightly constrain stellar ages, masses, compositions, and internal processes.
- OB Asteroseismology: SDSS-V will observe thousands of pulsating OB stars—including hundreds in eclipsing binaries—enabling detailed studies of interior mixing, angular momentum transport, tidal interactions, and binarity in massive stars.
- RGB Asteroseismology: Red giants with asteroseismic data are our best clocks for tracing Galactic evolution. SDSS-V will obtain spectra for >95% of bright (H<11) red giants in the TESS CVZs, enabling precise age and mass determinations across the Galaxy.
To date, these programs have focused on specific subclasses of stars or small samples in particular regions of the Galaxy. SDSS-V will provide the spectroscopic observations necessary for precise age measurements for hundreds of thousands of bright stars with seismic information across the Milky Way, primarily from TESS. In particular, SDSS-V will observe >95% of the bright (H<11) red giants in the TESS CVZs.
Massive Stars
SDSS-V will collect multi-epoch observations of hot, OBAF stars across the Galaxy and particularly in the TESS Continuous Viewing Zone (CVZ). Known eclipsing binary systems will be observed at least epochs, to identify stars for complete orbit determination and to compare dynamical masse and radii with seismic-derived values. Non-eclipsing systems will also be monitored for RV variability. Outside of the CVZ footprints, we expect to survey virtually all of the OB stars within 8 kpc of the Sun.
White Dwarfs
White dwarfs—stellar remnants of low- and intermediate-mass stars—encode vital information about stellar and planetary evolution and serve as laboratories for extreme physics. SDSS-V will target ~200,000 Gaia-selected white dwarfs to determine their masses, ages, compositions, and magnetic fields. These data will constrain mass loss in stellar evolution, calibrate star-formation histories, probe planetary system remnants, and test extreme physics such as dense matter and strong magnetic fields.
Stellar System Architecture
Most stars are born in multiple systems. SDSS-V will characterize the full architecture of stellar and substellar companions—stars, compact objects, brown dwarfs, and planets—across a range of environments and evolutionary stages.
- Multi-Star and Planetary Systems: The “Binaries Across the Galaxy” survey will measure multi-epoch radial velocities for tens of thousands of stars, revealing binaries across masses, separations, and Galactic environments, and probing how multiplicity relates to stellar evolution.
- TESS Planet Hosts: SDSS-V will provide high-resolution infrared spectra of thousands of TESS planet-host candidates, focusing on M dwarfs. These data will refine stellar properties, enabling robust interpretations of planetary parameters and habitability.
- White Dwarf Binaries: Compact white dwarf binaries underpin many transient phenomena and gravitational wave sources. SDSS-V will build an unbiased sample of ~10,000 such systems, providing critical insights into binary evolution, thermonuclear supernova progenitors, and compact object formation pathways.
Synergy with TESS
Together, SDSS-V and NASA’s TESS mission form a groundbreaking platform for stellar astrophysics. Key synergies include:
- High-resolution spectroscopy of TESS planet-host candidates
- Spectroscopic coverage of nearly all bright TESS targets in the CVZs
- Precision age dating of red giants with asteroseismic data
- Radial velocity monitoring of stellar and planetary systems
- Dynamical mass measurements for eclipsing binaries
This joint dataset will revolutionize our understanding of stars, planets, and the Galaxy.