Charles Townes, the University of California-Berkeley Nobel Prize physicist, was flying at 41,000 feet aboard a NASA plane 20 years ago, on the hunt for evidence that a monstrously powerful black hole was lurking in the heart of the Milky Way galaxy.
With him on those flights was his German postdoctoral student, Reinhard Genzel, and a team of other scientists trying to discover whether the invisible object was gulping entire stars and cosmic gases under the tug of its own irresistible gravity.
If that “supermassive” black hole did exist, Townes and Genzel knew, it would provide an extraordinary opportunity to study the dynamics of gravitational forces and the behavior of matter under those immense pressures, and could also help clarify many aspects of Albert Einstein’s theory of general relativity.
Thursday, Genzel, together with more than 20 other astronomers and physicists, are reporting they have finally found the strongest evidence yet that indeed a dense black hole, more than 3 million times as massive as our sun, does exist at the center of the Milky Way.
After tracking the paths of several stars in the vicinity of the presumed black hole for the past 10 years, Genzel’s team discovered last spring that at least one bright star is clearly hurtling in an orbit that could ultimately end in the star’s violent death within the black hole.
“It was one of those ‘wow’ experiences you rarely have as a scientist, but which makes being a researcher so rewarding,” said Genzel, now a professor at the Max Planck Institute for Extraterrestrial Physics in Germany, but who spends a quarter of each year as a physics professor at Berkeley. His group’s discovery is being reported in Thursday’s issue of the journal Nature.
The star appears to be speeding around the black hole at more than 3,000 miles a second at a distance roughly equal to the diameter of Earth’s solar system, he said. It will take about 15.2 years to complete its current orbit.
The mystery object at the very center of the Milky Way, surrounded by bursts of radio noise, is known as SgA because it appears to lie in the southern hemisphere constellation Sagittarius (“The Archer”).
Although such black holes have long been suspected in the centers of many other far-off galaxies, the existence of a “supermassive” black hole in our own Milky Way has been highly controversial. But this new evidence from Genzel’s group “makes it very difficult for anyone to say it’s not a black hole, and the doubters will now have to give up their doubts,” Townes said.