Sagittarius A*
The supermassive black hole at the heart of our galaxy.
Overview
Sagittarius A* (Sgr A*) is the 4-million-solar-mass supermassive black hole at the center of the Milky Way, 26,000 light-years from Earth.
Why It Matters
Sgr A* is the closest supermassive black hole — our laboratory for studying accretion, relativity, and the black hole/galaxy connection.
Scientific Explanation
Stars like S2 orbit Sgr A* every 16 years at up to 3% light speed, proving the central mass is compact. EHT imaged its shadow in 2022. It accretes quietly compared to quasars — a 'starving' giant flaring occasionally when matter falls in.
Historical Background
Radio source Sgr A* identified 1974. Ghez and Genzel shared Nobel (2020) for stellar orbit evidence. EHT collaboration produced first image (2022).
Visual Explanation
Keplerian orbits of S-stars tighten near invisible center. EHT ring matches GR predictions for 4M☉ at 26 kly.
Key Discoveries
- ✦ Stellar orbits prove 4×10⁶ M☉ central object
- ✦ Nobel Prize for galactic center supermassive BH
- ✦ EHT images Sgr A* shadow
- ✦ G2 cloud encounter (2014) tested accretion
Important Astronomers
Reflection Prompt
A monster lurks at the heart of our galaxy — yet the Milky Way thrives. How do black holes both destroy and create?
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