Our sun is in a quiet suburb, but the center, about 27,000 light-years away, is where most of the activity takes place.
This amazing shot shows the cosmic light show taking place there. With ordinary telescopes, there’s not much to see: a dust cloud obscures the view of the center of the Milky Way. Instead, we see high-energy X-rays (displayed in green, orange, and violet) and radio radiation (in shades of grey). The image combines measurements from NASA’s Chandra X-ray satellite with observations from the MeerKAT radio observatory in South Africa.
Most of the X-rays come from bubbles of hot gas, which were long ago imploded by supernovae, and from small, compact neutron stars. But the exact center of the Milky Way also produces X-rays. It comes from hot gas accumulating outside the edge of a supermassive black hole. This black hole is 4.3 million times the mass of the Sun. Giant stars and filaments of gas swirl around, regularly devouring matter from their environment.
It was already known that these X-rays show rapid flashes throughout the day. But there is also a large long-term variance. A team of astronomers led by Salvadoran astronomers Alexis Andres and Natalie Degenar of the University of Amsterdam has studied measurements taken by the Swift satellite over the past 15 years. Their research shows that the width of X-ray light at the center of the Milky Way between 2008 and 2012 was much less fluctuating than before and after. Nobody knows how it happened yet.
Another research team, led by Xu Zhang of Bard College in New York, looked at the reflection of X-ray light from gas clouds away from the black hole. From those X-rays, Zhang and her colleagues concluded that a very powerful eruption had occurred at the beginning of the 20th century, about 110 years ago.
Now waiting for another blast. An X-ray image of the center of the Milky Way will look very different. It could happen at any moment.
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