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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →The Milky Way’s Galactic Center is the crowded central region of our galaxy, in the direction of Sagittarius. At its heart is Sagittarius A* (pronounced “Sagittarius A-star”), a supermassive black hole about four million times the Sun’s mass. It is active because gas and dust around it move inward and emit changing radiation, including flares—but it is comparatively faint, not a brilliant quasar-like nucleus.
What is the Galactic Center?
The Galactic Center is a region, not just a black hole. It contains dense concentrations of stars, gas, and dust. Its central compact object, Sagittarius A*, lies about 27,000 light-years from Earth, obscured from ordinary visible-light views by intervening material. NASA’s Jet Propulsion Laboratory gives the distance to the Sgr A* environment as about 27,000 light-years.
What is Sagittarius A*?
Sagittarius A* (Sgr A*) is the compact radio source associated with the Milky Way’s central supermassive black hole. NASA describes its mass as approximately four million times the Sun’s mass. Its gravitational pull is inferred in part from the motions of stars orbiting close to it; the black hole is not a solid object that astronomers can photograph directly. NASA Science’s overview of black holes explains the distinction between a black hole and the material around it.
Why is the Galactic Center active?
Gas and dust near Sgr A* orbit in a changing environment. Some material moves inward toward the black hole, forming an accretion flow. The material around the event horizon—not light escaping from inside it—emits radiation as its conditions change. X-ray observations help astronomers study hot gas and estimate how much material from nearby stars approaches the black hole; infrared observations trace flares from material in the accretion disk. NASA’s Webb report describes a continuing stream of flares, with no observed periods of rest.
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Flares are observed; their exact triggers remain uncertain
A flare is a temporary increase in emitted radiation. Webb observations establish that Sgr A*’s surroundings flare repeatedly, but the reviewed observations do not establish one settled physical trigger for every event. Magnetic activity in the accretion flow is one area of investigation. NASA has compared the behavior with solar magnetic activity, but the comparison is an analogy: the Sun and a black hole’s accretion disk are very different physical systems.
Does “active” mean the Milky Way has a bright active galactic nucleus?
No. “Active” here means that material around Sgr A* emits variable radiation as it moves and changes—not that the Milky Way’s center shines like a luminous quasar. Bright active galactic nuclei are powered by large amounts of infalling matter. NASA characterizes the Milky Way’s black hole as comparatively subdued beside these much more luminous systems. Activity and exceptional brightness are not the same thing.
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How do astronomers observe the Galactic Center through dust?
Dust makes visible-light views difficult, so astronomers use wavelengths that reveal different parts of the environment. Infrared observations can track stars and flares through dust. X-ray observations help reveal hot gas and accretion activity. Radio observations provide a view of emission close to Sgr A*.
The Event Horizon Telescope (EHT), a network of radio telescopes around the globe, produced an image of Sgr A*. It shows radio emission from the region around the black hole and the black hole’s shadow—not a conventional photograph of an interior or a glowing event-horizon surface. ESO and its partners explain the EHT result in their Sgr A* image release.
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What do stars reveal about the black hole?
Stars near the Galactic Center orbit the compact object, letting astronomers measure its gravitational influence. By tracking those orbits over many years, they can infer the mass concentrated at the center. ESO reports that the star S2 passed within 17 light-hours of Sgr A* at its closest approach. This is an orbital measurement, not the black hole’s distance from Earth. ESO’s account of S2’s close approach describes the observations.
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