The similarity of the two images is striking because small stars and small galaxies look and behave very differently than large stars or galaxies. Black holes are the only objects in existence that only answer to one law of nature – gravity. And gravity does not care about scale.
For the last few decades, astronomers have thought that there are massive black holes at the center of almost every galaxy. While M87* is an unusually huge black hole, Sagittarius A* is likely pretty similar to many of the hundreds of billions of black holes at the center of other galaxies in the universe.
5. What scientific questions can this answer?
There is a lot more science to be done from the data the team collected.
One interesting avenue of inquiry stems from the fact that the gas surrounding Sagittarius A* is moving at close to the speed of light. Sagittarius A* is relatively small, and matter trickles into it very slowly – if it were the size of a human, it would consume the mass of a single grain of rice every million years. But by taking many images, it would be possible to watch the flow of matter around and into the black hole in real time. This would allow astrophysicists to study how black holes consume matter and grow.
A picture is worth a thousand words, and this new image has already generated 10 scientific papers. I expect there will be many more to come.
Chris Impey, University Distinguished Professor of Astronomy, University of Arizona
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