The Galactic Center massive black hole and nuclear star cluster

2010/06/30 by Reinhard Genzel, R. Genzel, Frank Eisenhauer +2 · 1,232 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Black hole (networking) #Galactic Center #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intermediate-mass black hole #Milky Way #Physics #Star cluster #Stars #Stellar black hole #astro-ph.GA

paper · pdf · doi:10.1103/revmodphys.82.3121

published in Reviews of Modern Physics 82(4), 3121-3195 (American Physical Society) · accepted by Rev.Mod.Phys. Aug 30, 2010

arxiv created 2010/09/27 · openalex publication_date 2010/12/20 · arxiv updated 2015/05/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

The Galactic Center is an excellent laboratory for studying phenomena and physical processes that may be occurring in many other galactic nuclei. The center of our Milky Way is by far the closest galactic nucleus, and observations with exquisite resolution and sensitivity cover 18 orders of magnitude in energy of electromagnetic radiation. Theoretical simulations have become increasingly more powerful in explaining these measurements. This review summarizes the recent progress in observational and theoretical work on the central parsec, with a strong emphasis on the current empirical evidence for a central massive black hole and on the processes in the surrounding dense nuclear star cluster. Current evidence is presented, from the analysis of the orbits of more than two dozen stars and from the measurements of the size and motion of the central compact radio source, Sgr A*, that this radio source must be a massive black hole of about 4.4\ifmmode×\else\texttimes\fi10⁶M_\astrosun, beyond any reasonable doubt. What is known about the structure and evolution of the dense nuclear star cluster surrounding this black hole is reported, including the astounding fact that stars have been forming in the vicinity of Sgr A* recently, apparently with a top-heavy stellar-mass function. A dense concentration of fainter stars centered in the immediate vicinity of the massive black hole are discussed, three of which have orbital peri-bothroi of less than one light day. This ``S-star cluster'' appears to consist mainly of young early-type stars, in contrast to the predicted properties of an equilibrium ``stellar cusp'' around a black hole. This constitutes a remarkable and presently not fully understood ``paradox of youth.'' What is known about the emission properties of the accreting gas onto Sgr A* is also summarized and how this emission is beginning to delineate the physical properties in the hot accretion zone around the event horizon.

Citations

• An overview of the high-energy emission from the Galactic Center
• Galactocentric Distance with the OGLE and [ITAL]Hipparcos[/ITAL] Red Clump Stars
• Dynamical evolution of the young stars in the Galactic center
• Key questions about Galactic Center dynamics
• Accretion and ejection in Sgr A*
• Structure of Sagittarius A* at 86 GH[CLC]z[/CLC] using VLBI Closure Quantities
• Hypervelocity Stars and the Galactic Center
• The Proper Motion of Sagittarius A*. II. The Mass of Sagittarius A*
• The Impact of Stellar Collisions in the Galactic Center
• Concerning the Distance to the Center of the Milky Way and its Structure
• Cluster Core Dynamics in the Galactic Center
• Stellar and wind properties of massive stars in the central parsec of the Galaxy
• Intraday Variation of Sagittarius A* at Short Millimeter Wavelengths
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• THE INFLUENCE OF DARK MATTER HALO ONTO EVOLUTION OF SUPERMASSIVE BLACK HOLE
• An Extended Star Formation History for the Galactic Center fromHubble Space TelescopeNICMOS Observations
• Diffuse X‐Ray Emission in a DeepChandraImage of the Galactic Center
• The Distribution of Stars near the Supermassive Black Hole in the Galactic Center
• Confirmation and Analysis of Circular Polarization from Sagittarius A*
• MHD SIMULATIONS OF ACCRETION ONTO Sgr A*: QUIESCENT FLUCTUATIONS, OUTBURSTS, AND QUASIPERIODICITY
• Discovery of Variable Iron Fluorescence from Reflection Nebulae in the Galactic Center
• Advection-dominated Accretion: Underfed Black Holes and Neutron Stars
• Stellar Remnants in Galactic Nuclei: Mass Segregation
• A size of ∼1 au for the radio source Sgr A* at the centre of the Milky Way
• EVIDENCE FOR WARPED DISKS OF YOUNG STARS IN THE GALACTIC CENTER
• The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth
• The Minispiral in the Galactic Center revisited
• Proper Motion of the Compact, Nonthermal Radio Source in the Galactic Center, Sagittarius A*
• Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• The First Stellar Abundance Measurements in the Galactic Center: The M Supergiant IRS 7
• DYNAMICAL AND EVOLUTIONARY CONSTRAINTS ON THE NATURE AND ORIGIN OF HYPERVELOCITY STARS
• The Linear Polarization of Sagittarius A*. I. VLA Spectropolarimetry at 4.8 and 8.4 GHz
• AN ALTERNATIVE ORIGIN FOR HYPERVELOCITY STARS
• The Need for a Second Black Hole at the Galactic Center
• Interferometric Measurements of Variable 340 GHz Linear Polarization in Sagittarius A*
• The Position of Sagittarius A*. III. Motion of the Stellar Cusp
• SimultaneousChandra, CSO, and VLA Observations of Sgr A*: The Nature of Flaring Activity
• Simulations of star formation in a gaseous disc around Sgr A* - a failed active galactic nucleus
• Stellar Dynamics at the Galactic Center with an Extremely Large Telescope
• AChandraStudy of Sagittarius A East: A Supernova Remnant Regulating the Activity of Our Galactic Center?
• Viewing the Shadow of the Black Hole at the Galactic Center
• Periapsis and gravitomagnetic precessions of stellar orbits in Kerr and Kerr–de Sitter black hole spacetimes
• On the orientation of the Sagittarius A* system
• Star Formation Around Supermassive Black Holes
• The Effect of Mass Segregation on Gravitational Wave Sources near Massive Black Holes
• On the Nature of the Variable Infrared Emission from Sagittarius A*
• Intraday Variability of Sagittarius A* at 3 Millimeters
• Reconstruction of Stellar Orbits Close to Sagittarius A*: Possibilities for Testing General Relativity
• Formation of Massive Black Holes in Dense Star Clusters. I. Mass Segregation and Core Collapse
• Discovery of an Unbound Hypervelocity Star in the Milky Way Halo
• Detection of Hard X-Ray Emission from the Galactic Nuclear Region with INTEGRAL
• Intense sub-arcsecond structure in the galactic center
• Dark Matter Annihilation at the Galactic Center
• Faraday Rotation in Global Accretion Disk Simulations: Implications for Sgr A*
• On the fate of gas accreting at a low rate on to a black hole
• The structure of the nuclear stellar cluster of the Milky Way
• TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VI. GALACTIC STRUCTURE, FUNDAMENTAL PARAMETERS, AND NONCIRCULAR MOTIONS
• On the Nature of the Compact Dark Mass at the Galactic Center
• A New X‐Ray Flare from the Galactic Nucleus Detected with theXMM‐NewtonPhoton Imaging Cameras
• Stellar orbit constraints on neutralino annihilation at the galactic center
• Really Cool Stars and the Star Formation History at the Galactic Center
• Polarimetry of near-infrared flares from Sagittarius A*
• Hubble Space Telescope/NICMOS Observations of Massive Stellar Clusters near the Galactic Center
• The Arches Cluster Mass Function
• The neutrino mass bound from WMAP 3 year data, the baryon acoustic peak, the SNLS supernovae and the Lyman-α forest
• Dark Matter Spikes and Annihilation Radiation from the Galactic Center
• Massive Star Formation in the Molecular Ring Orbiting the Black Hole at the Galactic Center
• Thermal X‐Ray Iron Line Emission from the Galactic Center Black Hole Sagittarius A*
• The Ecology of Star Clusters and Intermediate‐Mass Black Holes in the Galactic Bulge
• XMM-Newtonobservations of Sagittarius A East
• A self-gravitating accretion disk in Sgr A* a few million years ago: Is Sgr A* a failed quasar?
• Formation of Galactic Nuclei
• 3C 273 : A Star-Like Object with Large Red-Shift
• MeV Dark Matter: Has It Been Detected?
• Hydrodynamical Accretion onto Sagittarius A* from Distributed Point Sources
• SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light‐Month
• Hard X-ray view of the past activity of Sgr A^⋆ in a natural Compton mirror
• Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits
• The nucleus of our Galaxy
• A Relationship between Nuclear Black Hole Mass and Galaxy Velocity Dispersion
• Stellar orbits near Sagittarius A
• Nuclear Activity in Nearby Galaxies
• Testing properties of the Galactic center black hole using stellar orbits
• The Galactic center as a dark matter gamma-ray source
• Getting a Kick out of the Stellar Disk(s) in the Galactic Center
• TheK‐Band Spectrum of the Hot Star in IRS 8: An Outsider in the Galactic Center?
• K-band polarimetry of an Sgr A* flare with a clear sub-flare structure
• Using close stars as probes of hot accretion flow in Sgr A*
• Observation of Gamma Rays from the Galactic Center with the MAGIC Telescope
• A polarized infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
• Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks
• Theory of Star Formation
• The Nature of the 10 kilosecond X-ray flare in Sgr A*
• First simultaneous NIR/X-ray detection of a flare from Sgr A*
• Production of hypervelocity stars through encounters with stellar-mass black holes in the Galactic Centre
• X-ray flares reveal mass and angular momentum of the Galactic Center black hole
• ISO-SWS Observations of OMC-1: H₂ and Fine Structure Lines
• The extreme luminosity states of Sagittarius A*
• Three-body encounters in the Galactic Centre: the origin of the hypervelocity star SDSS J090745.0+024507
• A New Look at the Binary Characteristics of Massive Stars
• The Stellar-Dynamical Search for Supermassive Black Holes in Galactic Nuclei
• The solar chemical composition
• X-ray hiccups from Sagittarius A* observed by XMM-Newton - The second brightest flare and three moderate flares caught in half a day

Cited by

• Matière noire et (ou) gravitation modifiée : une approche historique et épistémologique
• Numerical simulations of the dark universe: State of the art and the next decade
• Counter-rotating stellar discs around a massive black hole: self-consistent, time-dependent dynamics
• f(R)gravity after the detection of the orbital precession of the S2 star around the Galactic Center massive black hole
• Accretion onto Stars in the Disks of Active Galactic Nuclei
• Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
• The γ-ray afterglows of tidal disruption events
• Stationary Black Holes: Uniqueness and Beyond
• Strong gravitational lensing in a spacetime with topological charge within the Eddington-inspired Born-Infeld gravity
• The former companion of hyper-velocity star S5-HVS1
• Quasinormal modes of black holes embedded in halos of matter
• Stellar Transits across a Magnetized Accretion Torus as a Mechanism for Plasmoid Ejection
• Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA
• Core-collapse supernovae in binaries as the origin of galactic hyper-runaway stars
• Mass distribution in the Galactic Center based on interferometric astrometry of multiple stellar orbits
• 2D kinematics of massive stars near the Galactic Centre
• The Milky Way's nuclear star cluster and massive black hole
• Near-infrared spectroscopic observations of massive young stellar object candidates in the central molecular zone
• THREE-DIMENSIONAL STELLAR KINEMATICS AT THE GALACTIC CENTER: MEASURING THE NUCLEAR STAR CLUSTER SPATIAL DENSITY PROFILE, BLACK HOLE MASS, AND DISTANCE
• Gravitational lensing and frame dragging of light in the Kerr–Newman and the Kerr–Newman (anti) de Sitter black hole spacetimes
• The Milky Way’s Supermassive Black Hole: How Good a Case Is It?
• Spin and mass of the nearest supermassive black hole
• Testing the black hole no-hair theorem with Galactic Center stellar orbits
• Non-thermal filaments from the tidal destruction of clouds in the Galactic centre
• Probing the interstellar dust towards the Galactic Centre: dust-scattering halo around AX J1745.6−2901
• On the rotation of nuclear star clusters formed by cluster inspirals
• Free motion around black holes with discs or rings: between integrability and chaos – III
• Motion in time-periodic backgrounds with applications to ultralight dark matter halos at galactic centers
• Weak annihilation cusp inside the dark matter spike about a black hole
• Gravitational lensing in black-bounce spacetimes
• Testing the Galactic Centre potential with S-stars
• An artificial neural network to discover hypervelocity stars: candidates in Gaia DR1/TGAS
• Discovery of a star sensitive to the spin of Sgr A*