Astronomers using NASA’s Hubble Space Telescope have captured images of a distant galaxy that houses a supermassive black hole. The giant galaxy NGC 4889 is located about 300 million light-years away in the Coma Cluster. The elliptical galaxy harbors in its heart a supermassive black hole whose mass is 21 billion times that of the Sun.
The black hole’s event horizon is about 130 billion kilometers
Astronomers at the European Space Agency said in a statement that the black hole’s event horizon is 81 billion miles. That is 15 times the diameter of Neptune’s orbit from the Sun. The event horizon is an area so powerful and dense that even light cannot escape its gravitational pull. However, the newly discovered black hole is well past its time of swallowing stars, gas and dust. Scientists said it was currently in a dormant stage.
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It has now stopped feeding after “feasting on NGC 4889’s cosmic cuisine” for a long time. Researchers said the environment within the galaxy NGC 4889 was now so peaceful that new stars were forming from the remaining gas and orbiting around the back hole. During the time it was active, the supermassive black hole was fueled by a process called hot accretion.
How scientists observed the supermassive black hole
When cosmic gas, dust and debris fell inwards toward the black hole, it accumulated to form an accretion disk. This spinning disk was accelerated by the gigantic black hole’s gravitational pull. It was heated to millions of degrees before expelling gigantic and energetic jets. During its active period, scientists would have classified the galaxy as a quasar, with the spinning disk around the supermassive black hole emitting a thousand times the energy output of our galaxy.
A black hole cannot be observed directly because visible light cannot escape its gravitation pull. But its mass can be determined indirectly. Astronomers used instruments on the Keck II Observatory and Gemini North Telescope to measure the velocity of stars moving around the center of NGC 4889. These velocities depend on the mass of the object they are orbiting. The specific velocities of stars allowed astronomers to calculate the mass of the supermassive black hole.