American, Japanese and European satellites, they have solved the long-standing mystery why is our galaxy’s black hole
We have wondered why the Milky Way’s black hole appears to be a slumbering giant. But now we realise that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst,"
Between 1994 and 2005, revealed that clouds of gas near the central black hole brightened and faded quickly in X-ray light as they responded to X-ray pulses emanating from just outside the black hole. These X-ray pulses take 300 years to traverse the distance between the central black hole and a large cloud known as Sagittarius B2, so the cloud responds to events that occurred 300 years earlier. But after the X-ray pulse passes through, the cloud fades to its normal brightness. "By observing how this cloud lit up and faded over ten years, we could trace back the black hole’s activity 300 years ago. The black hole was a million times brighter three centuries ago.