Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Flares near edge of our galaxy’s central black hole indicate rapid spin

31.10.2003


Razor-sharp optics on ground-based telescopes now allows astronomers to peer at events occurring near the very edge of our galaxy’s central black hole, providing new clues about the massive but invisible object at the core of the Milky Way.


The whirling accretion disk surrounding the supermassive black hole (center) at the core of the Milky Way Galaxy. As hot gas falls into the black hole, the energy is converted into radiation which is emitted in sudden bursts. The infrared emissions detected recently may accompany blobs of gas ejected from the disk (purple) or come from sparks that occur randomly in the accreting gas (yellow). (Courtesy of Nature, based on image created by Michael P. Owen)



In a paper in this week’s issue of Nature, a team led by University of California, Berkeley, physicist Reinhard Genzel, who also directs the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, reports the detection of powerful infrared flares from a region just outside the supermassive black hole.

If the black hole, which has a mass about 3.6 million times that of the sun, were at the center of our solar system, the flares would have come from somewhere within the orbit of Earth.


The observed signals, rapidly flickering on a scale of minutes, probably came from hot gas falling into the black hole, just before the gas disappeared below the "event horizon" - the point of no return for a black hole from which even light cannot escape.

The new observations strongly suggest that the black hole at the galaxy’s core rotates rapidly, the team concluded.

"This is a major breakthrough," Genzel said. "We know from theory that a black hole can only have mass, spin and electrical charge. Last year, we were able to unambiguously prove the existence and determine the mass of the galactic center black hole.

"If our assumption is correct that the periodicity (of the flares) is the fundamental orbital time of the accreting gas, we now have also measured its spin for the first time. And that turns out to be about half of the maximum spin that general relativity allows."

The observed flares repeated about every 17 minutes, implying that the central black hole rotates once about every 30 seconds, said Eliot Quataert, a UC Berkeley assistant professor of astronomy involved in theoretical modeling of the black hole accretion disk. For comparison, the sun, which is one-tenth the diameter of the black hole and several million times less massive, rotates about once every month, Quataert noted.

Scientists have never before been able to study phenomena in the immediate neighborhood of a black hole in such a detail. The new result is based on observations obtained with the NACO Adaptive Optics instrument on the 8.2-meter KUEYEN telescope of the European Southern Observatory’s Very Large Telescope (VLT) in Chile’s Atacama desert.

A separate team from UCLA reported last month in Astrophysical Journal that it had seen similar variability in infrared emissions from the galaxy’s central black hole using the adaptive optics on the W. M. Keck II telescope in Hawaii. Adaptive optics allows telescopes to overcome the image distortions in the optical/infrared wavelength region caused by the turbulent terrestrial atmosphere. By flexing a deformable mirror, adaptive optics on the VLT produces an image about 10 times sharper in the near-infrared than with conventional observations, and about four times sharper than the Hubble Space Telescope working at this wavelength.

"Now the era of observational black hole physics has truly begun," Genzel said.

"These observations, reflecting similar patterns seen earlier in X-rays, open a new window on this enigmatic source," said Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics, in a commentary that also appears in this week’s Nature.

"We had been looking for infrared emission from that black hole for more than a decade," said team member Andreas Eckart of Cologne University in Germany. "We were certain that the black hole must be accreting matter from time to time. As this matter falls towards the surface of the black hole, it gets hotter and hotter and starts emitting infrared radiation."

The near-infrared emissions were observed on May 9, 2003, coming from a bright radio source at the galactic core known as Sagittarius A*, or SgrA*.

"Our data give us unprecedented information about what happens just outside the event horizon and let us test the predictions of general relativity," explained Daniel Rouan, a team member from Paris-Meudon Observatory in France. "The most striking result is an apparent 17-minute periodicity in the light curves of two of the detected flares. If this periodicity is caused by the motion of gas orbiting the black hole, the inevitable conclusion is that the black hole must be rotating rapidly."

The rapid variability seen in the infrared data indicates that the region around the event horizon must have chaotic properties very much like those seen in thunderstorms or solar flares, the researchers said. In fact, wrote Narayan in his Nature commentary, the flares could be created by the same magnetic phenomenon, magnetic reconnection, that produces bright flares on the sun.

"The beauty of having a flaring source such as Sgr A* is that each flare provides a new and independent view of the underlying physical processes," he wrote. "So by collecting and studying data on many flares, we may learn much more than from a steady source."

Genzel’s coauthors, in addition to Eckart and Rouan, are Rainer Schödel, T. Ott and B. Aschenbach of the Max-Planck Institute, T. Alexander of the Weizmann Institute of Science in Israel, and F. Lacombe of the Observatoire de Paris.

Robert Sanders | UC Berkeley News
Further information:
http://www.berkeley.edu/news/media/releases/2003/10/29_flares.shtml
http://www.berkeley.edu/news/media/releases/2002/10/23_bhole.html

More articles from Physics and Astronomy:

nachricht Two dimensional circuit with magnetic quasi-particles
22.01.2018 | Technische Universität Kaiserslautern

nachricht Meteoritic stardust unlocks timing of supernova dust formation
19.01.2018 | Carnegie Institution for Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Thanks for the memory: NIST takes a deep look at memristors

22.01.2018 | Materials Sciences

Radioactivity from oil and gas wastewater persists in Pennsylvania stream sediments

22.01.2018 | Earth Sciences

Saarland University bioinformaticians compute gene sequences inherited from each parent

22.01.2018 | Life Sciences

VideoLinks Wissenschaft & Forschung
Overview of more VideoLinks >>>