Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Magnetic Explosions in the Distant Universe

09.02.2007
Long duration gamma-ray bursts (GRBs), first discovered in the 1970s, are the most explosive events in the Universe. Finding out what happens during these cataclysmic events is a major challenge, partly because they usually occur at the edge of the visible Universe and partly because the bursts last only a matter of seconds.

Observations accumulated over the last decade have led to a consensus that at least some GRBs mark the death throes of a giant star as its core collapses to form a black hole. Until now, it has generally been thought that the black hole ejects a jet of plasma (extremely hot gas) which is blasted outwards at close to the speed of light.

This theory is called into question by a new study led by Pawan Kumar from the University of Texas. The work has been accepted for publication in the journal, ‘Monthly Notices of the Royal Astronomical Society’.

MAGNETIC OUTFLOW

Scientists have long speculated that the gamma-ray emission we see comes from fluctuations in the speed of the ejected material. The faster and slower ejecta collide, producing shocks in the jet which result in the emission of gamma-rays. Although this internal shock model is the standard explanation, it relies on the jet consisting of ordinary matter -- the same sort of material that we are made from -- or what scientists call baryons.

Now, however, Pawan Kumar and colleagues have cast doubt on this model. Instead of the GRBs being generated by internal shocks, Kumar’s team finds that the jet is actually a powerful magnetic outflow which transports huge amounts of energy away from the collapsed star.

Using data from the Swift satellite, Professor Kumar’s team has analysed a sample of 10 gamma-ray bursts that were recorded between January 2005 and May 2006. In each case, Swift collected gamma-ray, X-ray and optical light immediately after the explosions were detected. Such multi-wavelength observations are essential if the researchers are to understand what happens after the brief burst fades and the source object is only visible in X-rays or visible light.

“Swift is uniquely capable of such simultaneous multi-wavelength observations,” said Neil Gehrels of NASA’s Goddard Space Flight Center, Principal Investigator for the Swift satellite.

The new study reveals the physical process responsible for the generation of gamma-ray radiation and the distance from the black hole where this radiation is produced.

"The gamma-ray source is located about 10 billion km from the black hole, or 100 times further than previously thought,” said Professor Kumar. “This and several other lines of evidence put forward in our work suggest that the outflow is dominated by the magnetic field.”

The data indicate that a magnetic jet decays into gamma-rays. The subsequent interaction (of the jet) with the surrounding gas causes intense heating and this produces an afterglow that is seen at X-ray and visible light wavelengths.

Dr. Paul O’Brien from the University of Leicester, a co-investigator on the project, said, “In just a few seconds gamma-ray bursts emit as much energy as the Sun does in 10 billion years. The Swift observations are telling us that this emission is due to an outflow in which magnetic fields transport the energy. If confirmed, this will alter our view of how these objects work.”

“Using the Swift data we can accurately measure the times when the prompt emission stops and the afterglow becomes visible,” said Richard Willingale, also from the University of Leicester. “These times constrain the distance of the emitting region from the black hole and hence the physical processes involved.”

Since its launch on 20 November 2004, Swift has observed over 200 gamma-ray bursts and provides prompt data on almost all of them.

“Swift can turn and observe a gamma-ray burst with its X-ray and optical telescopes in just a few tens of seconds,” said Professor David Burrows from Pennsylvania State University, lead investigator for the X-ray telescope on Swift. “This capability allows us to capture a snapshot of the early emission which carries information on the physical processes involved.”

Dr Silvia Zane, from the Mullard Space Science Laboratory said, “This is going to revolutionise our understanding of the cause of such explosions.”

Peter Bond | alfa
Further information:
http://www.ras.org.uk/

More articles from Physics and Astronomy:

nachricht The moon is front and center during a total solar eclipse
24.07.2017 | NASA/Goddard Space Flight Center

nachricht Superluminous supernova marks the death of a star at cosmic high noon
24.07.2017 | Royal Astronomical Society

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: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Ultrathin device harvests electricity from human motion

24.07.2017 | Power and Electrical Engineering

Scientists announce the quest for high-index materials

24.07.2017 | Materials Sciences

ADIR Project: Lasers Recover Valuable Materials

24.07.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>