Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Black hole sheds light on a galaxy

18.04.2008
Light echo of a high-energy flash from a black hole first observed in detail

A light echo occurs when interstellar gas is heated by radiation and reacts by emission of light. An international team led by Stefanie Komossa from the Max Planck Institute for extraterrestrial Physics in Garching, Germany, has observed the light echo of an enormous X-ray flare, which was almost certainly produced when a single star was disrupted by a supermassive black hole. For the first time, the light echo of such a rare and highly dramatic event could be observed in great detail. The light echo not only revealed the stellar disruption process, but it also provides a powerful new method for mapping galactic nuclei (Astrophysical Journal Letters, May 2008).


Illustration: MPE/ESA
The artistic view shows the light echo of a high-energy flash from a black hole

When a star is disrupted by a black hole in the nucleus of a galaxy, its debris is inevitably attracted and absorbed by the black hole. This sudden increase in the accretion rate causes an abrupt burst of ultraviolet and X-ray light because the gas from the disrupted star becomes very hot. As the high-energy radiation travels through the core of the galaxy it illuminates surrounding matter and so makes it possible to probe regions of the galaxy that would otherwise be unobservable.

“To study the core of a normal galaxy is like looking at the New York skyline at night during a power failure: You can’t learn much about the buildings, roads and parks”, says Stefanie Komossa. “The situation changes, for example, during a fireworks display. It’s exactly the same when a sudden burst of high-energy radiation illuminates a galaxy.” However the astronomers

had to hurry up and look through the telescope at the right moment, because X-ray bursts don’t last very long.

From the strength, the degree of ionization and the deduced velocities of the rapidly varying emission lines, the physicists can tell in which part of the galaxy they are emitted. The emission lines represent the “fingerprints” of the atoms in the hot gases heated by the flare. The galaxy with catalog name SDSSJ0952+2143 which was detected in December 2007 by Komossa and her team in the Sloan Digital Sky Survey archive caught their attention because of its superstrong iron lines: the strongest (relative to oxygen emission) that were ever observed in a galaxy. In them the authors see an evidence for a molecular torus which plays an important part in so-called unified models of active galaxies.

The unified model postulates that all active galaxies are made of identical components and that the perceived differences are just due to the different directions from which we view the galaxies. An important element of this model is the molecular torus, which surrounds the black hole and its accretion disk and covers them when viewed from certain directions. Also the breadth of the spectral lines which the scientists measure is influenced by the viewing direction and that means by the molecular torus.

Should the expectations of Komossa and her colleagues be confirmed, this will be the first time that scientists have seen such a strong time-variable signal from a molecular torus. From the light echo, the torus can be mapped and its geometry inferred, something which has not been possible up to now.

Along the same lines is the detection of variable emission in the infrared: It can be interpreted as the “last cry for help” of the heated dusty torus matter before the dust is destroyed by the flash.

In addition to the remarkably strong iron lines, the scientists also noticed a very peculiar shape of the hydrogen emission lines which had never been seen before. This line hints at activities of the disk of matter around the black hole, which consists mainly of hydrogen. “Probably we are seeing the debris of the disrupted star here which is just being accreted by the black hole”, explains Hongyan Zhou from the MPE, co-author of the research paper.

The recently-discovered light echo still continues and is being traced with powerful telescopes. The burst itself has faded away. The first observations with the X-ray satellite Chandra show measurable but already faint X-ray light from the galactic nucleus.

“Reverberation-mapping of light echoes opens up new possibilities to study galaxies”, concludes Komossa. The team now wants to use this method to explore the physical conditions in the circumnuclear material in active and non-active galaxies.

Original paper: http://xxx.lanl.gov/abs/0804.2670

Contact:

Dr. Mona Clerico
Press Officer
Max Planck Institute for Astrophysics and Max Planck Institute for extraterrestrial Physics

Phone +49 89 30000-3980 Email: clerico@mpe.mpg.de

Dr. Stefanie Komossa
Max Planck Institute for extraterrestrial Physics
Phone +49 89 30000-3577
Email: skomossa@mpe.mpg.de

Dr. Mona Clerico | Max-Planck-Gesellschaft
Further information:
http://www.mpe.mpg.de/main.html

More articles from Physics and Astronomy:

nachricht From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic 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: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>