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Sagittarius A*
Details
Sagittarius A* is the supermassive black hole at the center of the Milky Way. Event Horizon Telescope observations imaged the glowing material around it, resolving a radio source about 52 million kilometers across around a black hole of roughly 4.3 million solar masses.
Sagittarius A* is the hidden center of the Milky Way. It is a supermassive black hole, which means it is not a bright object with a surface but a gravitational anchor around which the galaxy’s inner motion is organized. What the eye sees is not the black hole itself, but the material responding to it.
That is why the Event Horizon Telescope image mattered so much. The glowing ring and surrounding radio source revealed the hot environment around Sagittarius A*, not a literal portrait of the object as if it were a planet or star. The black hole remains invisible in the ordinary sense, yet its influence is written into the light around it.
Sagittarius A* shows that the center of a galaxy can be known through motion and radiation even when the black hole itself stays hidden. It is the Milky Way’s central mass, the place where gravity is most decisive, and the reason the galaxy has a core that can be studied even when the core itself cannot be directly seen.
9.10million km
Visual creditscaleofspace.org / CC BY-NC 4.0
Key facts
- Category
- Black holes
- Object class
- Supermassive black hole
- Host
- Milky Way
- Scale fact
- 24.5 million kmevent horizon diameter
- Mass
- ~4.3 million solar masses
Scale context
Where Sagittarius A* sits on the full axis
Shared physical scale
24.7billion km
Together, these objects make the size change around Sagittarius A* easy to compare at a glance.
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.