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Our galaxy's giant black hole has a smaller sibling

NASA/JPL-Caltech/S. Stolovy (SSC/Caltech)

By studying the motions of a particularly dense cloud of gas, astronomers have inferred the existence of a new black hole near the center of the Milky Way galaxy. It's not confirmed yet, but it's estimated to weigh in at a whopping 100,000 times the mass of our sun.

That's big, but not the biggest — that title goes to Sagittarius A*, a supermassive black hole sitting in the middle of our galaxy that has a mass 4 million times greater than our sun.

Why it matters: This "intermediate" class of black hole provides clues to the formation of their bigger cousins. It seems that every galaxy hosts a giant black hole. How do these black holes form and grow? What's the connection between giant black holes and the evolution of their host galaxies? Having a "missing link" in our own backyard helps answer those questions.