Sagittarius A* vs M87* Black Hole Comparison
Compare the Event Horizon Telescope supermassive black holes Sagittarius A* (Milky Way) and M87* (Virgo Cluster) in mass, distance, and shadow size.
Compared Celestial Objects
Sagittarius A* (Galactic Center Black Hole)
Coordinates, GRAVITY S2 stellar orbit distance (8,277 pc) & mass (4.297 × 10^6 M☉), EHT 51.8 μas shadow, and Galactic Center guide for Sgr A*.
Constellation: Sagittarius · Coords: 17h 45m 40.04s, -29° 00′ 28.1″
Messier 87 (Virgo A Giant Elliptical Galaxy)
Coordinates, distance (16.4 Mpc / 53.5 Mly), EHT 6.5-billion M☉ black hole M87*, relativistic jet, and observing guide for Messier 87.
Constellation: Virgo · Coords: 12h 30m 49.42s, +12° 23′ 28.0″
Normalized Shared Parameter Table
| Parameter | Unit / Scale | Sagittarius A* (Galactic Center Black Hole) | Messier 87 (Virgo A Giant Elliptical Galaxy) |
|---|---|---|---|
| Black Hole Mass | M☉ | (4.297 ± 0.012) × 10⁶ M☉ | (6.5 ± 0.7) × 10⁹ M☉ |
| Heliocentric Distance | kpc / Mpc | 8.277 ± 0.009 kpc (27,000 ly) | 16.8 ± 0.7 Mpc (54.8 Mly) |
| EHT Shadow Ring Diameter | μas | 51.8 ± 2.3 μas | 42 ± 3 μas |
| Host Galaxy Optical Magnitude | mag | Obscured Galactic Center (Av ≈ 25 mag) | V = +8.63 ± 0.06 (giant elliptical M87) |
Astrophysical & Observational Synthesis
One of the most striking coincidences in observational astrophysics is that M87* is ~1,510 times more massive than Sagittarius A* (6.5 × 10⁹ M☉ vs 4.30 × 10⁶ M☉) and also lies ~2,030 times farther away (16.8 Mpc vs 8.28 kpc). Because the apparent angular size of a black hole's photon shadow scales linearly with M/D, both black holes subtend almost the same angular diameter on Earth's sky: 51.8 microarcseconds for Sgr A* and 42 microarcseconds for M87*.
Their accretion environments and dynamical timescales differ by three orders of magnitude: gas orbits Sgr A* in minutes (varying rapidly during a single EHT observing night) without launching a large-scale jet, whereas M87* varies over days to weeks and powers a 1.5-kiloparsec relativistic synchrotron jet visible in optical telescopes.
Related Reference Guides
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Proper Motion, Radial Velocity & Redshift
How astronomers combine tangential proper motion (mas/yr), Doppler radial velocity (km/s), and cosmological redshift (z) to reconstruct 3D space motion.
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
Primary Catalogs & Scientific Sources
- Event Horizon Telescope Collaboration Horizon-Scale Results (2019 ApJL 875 L1 & 2022 ApJL 930 L12): Event Horizon Telescope Collaboration 2019, ApJL, 875, L1; 2022, ApJL, 930, L12 — Event Horizon Telescope Collaboration
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC