TAU Scientists Help Discover the Most Massive Stellar Black Hole Ever Found

An international team, including astronomers from Tel Aviv University, has uncovered the most massive stellar black hole found to date in a binary system.

Published in the prestigious journal Nature this week, the research was conducted by an international team including Professor Tsevi Mazeh, who is the director of the Sackler Institute of Astronomy at Tel Aviv University and holds the Oren Family Chair of Experimental Physics, and his Ph.D. student Avi Shporer.

The newly-discovered black hole is about 16 times the mass of our sun and located three million light-years away in a distant galaxy called Messier 33. The finding is unique because the black hole, named M33 X-7, is associated with an unusually large companion star (its binary pair), with a mass about 70 times the mass of our sun. The two objects move one around the other in space once every 3.5 days in an everlasting dance.

A stellar black hole is formed from the collapse of the core of a massive star at the end of its life. The collapse creates an intense gravitational force, where not even rays of light can escape its gravitational pull, rendering the phenomenon invisible. Matter transferred from the companion star into the black hole falls into the hole’s gravitational attraction and emits X-ray radiation that the astronomers have detected by using special satellites.

“Giant telescopes and satellites make it possible for us to discover in space systems that seem to come from a science-fiction film,” says Prof. Mazeh. “We are able to study black holes whose existence we were able to imagine only thanks to Einstein's General Theory of Relativity.”

This new discovery raises all sorts of questions about how massive black holes are formed. Prof. Mazeh says that these questions illustrate the enormous scale of the universe and the smallness of the Earth within it. “I hope these discoveries will lead scientists and even human society to a degree of modesty,” he noted.

The scientific community has known about black holes orbiting companion stars for 40 years. “This discovery raises doubts about theories of how black holes, like this one, are created,” said Prof. Jerome Orosz from San Diego State University, the first contributor of the article. Prof. Orosz led the international teams that analyzed data collected by the Chandra X-ray satellite and the Gemini telescope in Hawaii.

Concludes Prof. Mazeh, “Astronomical measurements allow us to peek into the vastness of space and discover epic events incomparable with anything which takes place on earth.”