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 PPPL physicist uncovers clues to mechanism behind magnetic reconnection
24.01.2017 | DOE/Princeton Plasma Physics Laboratory

nachricht Electrocatalysis can advance green transition
23.01.2017 | Technical University of Denmark

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: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Arctic melt ponds form when meltwater clogs ice pores

24.01.2017 | Earth Sciences

Synthetic nanoparticles achieve the complexity of protein molecules

24.01.2017 | Life Sciences

PPPL physicist uncovers clues to mechanism behind magnetic reconnection

24.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>