Using the XMM Newton Observatory, the European Space Agency's new X-ray satellite telescope, an international team of researchers have found evidence of a supermassive black hole whose rotation is being slowed slightly by the action of magnetic fields present in the super hot gas surrounding the black hole.

This slowing action generates energy in much the same way that heat is generated by a car's brakes as they slow the rotation of the wheels.

"Our observations provide the first convincing evidence that the massive black holes found at the center of galaxies are spinning," said team member Christopher Reynolds, an assistant professor of astronomy at the University of Maryland. "These findings also provide the first observational evidence for a 25-year-old theory predicting the slowing of rotating black holes by magnetic fields," said Reynolds, who worked on the study while a researcher at the University of Colorado-Boulder.

Reynolds said the study team, which was led by Joern Wilms of Tuebingen University in Germany, realized they'd found something "new and unusual" when the spectrum of the x-rays they were seeing indicated a huge amount of energy was coming from gas very close to the black hole.

"This was surprising because one would expect the energy to come from a whole range of distances as a result of gas falling into the black hole," Reynolds said.

According to Reynolds, the expected source of x-rays near a black hole is energy released as gas is drawn into the black hole. Black holes are continually sucking in nearby interstellar gas and, as it is drawn in, the gas swirls around the black hole forming what astronomers call an accretion disk.

"Energy is given off by this process throughout the disk of swirling super-heated gas and not just from the region closest to the black hole," said Reynolds. "For that reason, we knew there must be a different source for the energy we were detecting. We believe that source is dissipation of the black hole's rotation by the braking action of magnetic fields. These magnetic fields are created by motions in the gas. As gas falls into the black hole it drags part of the magnetic field with it connecting the black hole to the spinning disk of gas. It is this connection that is believed to act as the drag, slowing the black hole's rotation."

Black holes are collapsed material that is so tightly compacted that not even light can escape once it is within the grasp of a black hole's gravitational field.

Astronomers believe supermassive black holes such as the one in this study are found at the center of every galaxy, while small stellar black holes are thought to be scattered throughout the universe.

This study, which has been accepted for publication in the Monthly Notices of the Royal Astronomical Society in London, provides the strongest evidence yet that supermassive black holes also spin. Small, stellar black holes were recently shown to have the ability to spin by scientists at NASA's Goddard Space Flight Center.

The supermassive black hole in this study, known as MCG-6-30-15, lies more than 120 million light-years from Earth. It contains material roughly equal to 10 million Suns compressed into an area smaller than our solar system.

The XMM Newton Observatory launched by ESA in 1999 can collect five times as many photons as NASA's Chandra X-Ray Observatory, which specializes in high-quality digital imagery, The XMM Newton thus allows researchers to study the emissions of supermassive black holes in unprecedented detail, according to Reynolds.

However, Reynolds noted that NASA has several X-ray observatories even more powerful than XMM Newton in the construction or planning phase. - By Lee Tune

(Editor's Note: Images and video animation of the black hole are available from the website of the NASA Goddard Space Flight Center at this URL.)


[Contact: Lee Tune ]

24-Oct-2001