Galactic Center

The central region of the Milky Way, containing the supermassive black hole Sagittarius A* amid dense concentrations of stars, gas, and dust.

Sagittarius A*: The compact radio source at the Milky Way’s center, identified as a supermassive black hole of about four million solar masses. It is the Galactic Center’s dominant compact object and anchors the surrounding stellar orbits.
Milky Way: The barred spiral galaxy that contains the Solar System and hundreds of billions of stars. The Galactic Center is the innermost region of this galaxy.
Event Horizon Telescope: A global network of radio telescopes that combines observations to image black-hole-scale structures. Its observations produced the first image of emission around Sagittarius A*.
Galactic bar: An elongated structure of stars and gas crossing the central region of a barred spiral galaxy. Its influence on gas flows may help explain how material reaches the inner Milky Way.
S-star cluster: A group of young stars on tight, fast orbits around Sagittarius A*. Their measured orbits provide direct evidence for a massive object confined to the center.
Galactic bulge: A dense, roughly spheroidal concentration of stars surrounding the center of a spiral galaxy. The Milky Way’s bulge surrounds and blends into its central region.
General relativity: Albert Einstein’s theory describing gravity as the curvature of spacetime caused by matter and energy. The S-star orbits and black-hole environment provide tests of relativistic predictions.
Fermi bubbles: Two enormous lobes of gamma-ray and other emission extending above and below the Milky Way’s plane. Their origin may involve past activity from the central black hole or intense star formation.
Central Molecular Zone: A dense concentration of molecular gas extending across the inner few hundred parsecs of the Milky Way. Its clouds supply the Galactic Center’s central environment with cold gas.
Interstellar medium: The gas and dust between stars in a galaxy. Its gas and dust shape the material and visibility of the central environment.

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