Death of a star

Scientists watch supernova in real-time

For the first time a star has been observed in real-time as it goes supernova a mind bogglingly powerful explosion as the star ends its life, the resulting cosmic eruption briefly outshining an entire galaxy. UK scientists, in collaboration with international colleagues, used NASA's Swift satellite and a combination of orbiting and ground-based observatories to catch a supernova in the act of exploding. The results, including an associated and intriguing Gamma Ray Burst [GRB], appear in 31 August issue of Nature.

The event began on the 18th February, 2006, in a star forming galaxy about 440 million light-years away toward the constellation Aries. At that time it was immediately realised that this was an unusual gamma-ray burst, about 25 times closer and 100 times longer than a typical gamma-ray burst. The burst lasted for almost 40 minutes as opposed to a typical GRB of a few milliseconds to tens of seconds. Because the burst was so long Swift was able to observe the bulk of the explosion with all three of its instruments: the Burst Alert Telescope, which detected the burst and relayed the location to ground observatories within 20 seconds; the X-ray telescope [XRT] and Ultraviolet/Optical Telescope [UVOT], which provide high-resolution imagery and spectra across a broad range of wavelengths.

"The fact that Swift can re-point very fast, slewing round to bring the XRT and UVOT to bear on the burst allowed us to get onto it very quickly indeed, enabling us to observe the critically important early behaviour of the event" remarked Dr. Alex Blustin from University College London's Mullard Space Science Laboratory [UCL/MSSL],

Careful, multi-wavelength analysis of space and ground-based observations has now revealed exactly what took place.

The exceptionally long burst, in the form of a jet of high-energy X-rays, pierced through the doomed star from its core and sent out a warning within minutes that a supernova was imminent. As the GRB faded away the massive star blew itself into smithereens.

"This GRB was the most extraordinary evolving object yet seen by Swift," said team member Dr. Paul O'Brien at the University of Leicester. "The three on-board telescopes all detected a slowly brightening then fading object. The results suggest a broad jet expanded into the surroundings but it was accompanied by a slower-moving and incredibly hot - two million degree - bubble of gas produced from the shock-wave of the exploding star".

Swift's three telescopes - covering gamma ray, X-ray, ultraviolet and optical wavelengths - captured X-rays fading to ultraviolet and then optical light, evidence of the shock wave from the explosion pushing exploded star material into the surrounding medium. Dr. Alex Blustin and colleague Dr. Mat Page, also from UCL/MSSL, conducted the analysis of Swift's ultra violet and optical data that tracked the expansion of the shock wave from the explosion.

Paul O'Brien added," This is the first time such an extraordinary event has been seen from a GRB. The thermal component of the supernova shock wave was clearly seen in this case as the GRB itself was fairly modest, some 100 times less than a typical GRB - a mere ten million billion times the power of the Sun!"

UK astronomers from the Universities of Leicester and Hertfordshire were part of a group led by Italy's National Institute for Astrophysics that used the European Southern Observatory's 8.2-metre Very Large Telescope [VLT] in Chile and the University of California's Lick Observatory Shane 3-metre telescope to obtain regularly-sampled optical spectroscopy of the shock wave. Two days later the classical supernova, a glowing cloud of gas powered by the decay of radioactive debris from the dead star, was beginning to outshine the fading shock wave.

Dr Andrew Levan, University of Hertfordshire said," As well as studying the early evolution of the supernova for the first time these observations also show how the material ejected in the explosion evolve in the following days and weeks, the timescales on which supernovae are normally studied". Dr. Levan added," This shows that the supernova associated with this GRB is a transition object, brighter than most supernovae in the universe, but fainter than those previously seen with GRB's. Understanding the reasons for this is a crucial step in understanding why only a small percentage of massive stars can create GRB's".

"Usually these events are not detected until after the supernova has brightened substantially in the optical wavelength, many days after the initial explosion", commented Prof. Keith Mason, UK lead investigator for the UVOT telescope on Swift and CEO of the Particle Physics and Astronomy Research Council [PPARC]," but on this occasion we were able to study the remarkable event in all its glory from the very beginning".

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Background Notes

Images For animation and a before-after image of the 18 February 2006 explosion visit:
http://www.nasa.gov/mission_pages/swift/bursts/oddball_burst.html

Contacts

Press Peter Barratt
PPARC Press Office
Tel: 01793 442025
Mobile: 07879 602899
Email: peter.barrat@pparc.ac.uk
Web: http://www.pparc.ac.http://Artcl/media_contacts.asp

Ather Mirza
University of Leicester
Tel: 0116 252 3335
am74@le.ac.uk

Judith H Moore
UCL Media Relations Manager
Tel: +44 (0) 20 7679 7678 (int: 07678)
Skype: judithhmoore
Mobile: +44 (0)77333 075 96
Out-of-hours: +44 (0)7917 271 364
Email: judith.moore@ucl.ac.uk
Web: http://www.ucl.ac.uk/media/

Lynn Cominsky
NASA Swift Press Officer, Sonoma State University
Tel: +00.1. 707.6642655
Email: lynnc@universe.sonoma.edu

Science Dr. Alex Blustin
University College London, Mullard Space Science Laboratory
Tel: 01483 204196
Out-of-hours: 01483 276241
Email: ajb@mssl.ucl.ac.uk

Dr. Mat Page
University College London, Mullard Space Science Laboratory
Tel: 01483 204283
Out-of-hours: 01403 257836
Email: mjp@mssl.ucl.ac.uk

Dr. Paul O'Brien
University of Leicester
Tel: 0116 252 5203
Mobile: 07891894071 Email: pto@star.le.ac.uk

Dr. Andrew Levan
University of Hertfordshire
Tel: 01707 281374
Email: A.Levan@star.herts.ac.uk

Dr. Nial Tanvir
University of Hertfordshire
Tel: 01707 2862899
Mobile: 07980 136499
Email: nrt@star.herts.ac.uk

Swift Launched in November 2004, Swift detects gamma-ray burst and X-ray flashes, and relays their coordinates to the scientific community within seconds. While SWIFT rapidly re-points to continue observations with its high resolution telescopes of the decaying X-ray, UV and optical afterglows that accompany these events, rapid follow-up observations may also be undertaken by other more powerful satellites such as Chandra, the Hubble Space Telescope or XMM satellites and by the European Southern Observatory's Very Large Telescope [VLT] and other major observatories. These powerful co-ordinated observation programmes, instigated by SWIFT, are slowly unravelling the mystery of star explosions.

Goddard Space Flight Centre in the US manages Swift, a NASA mission with participation of the Italian Space Agency [ASI] and the Particle Physics and Astronomy Research Council [PPARC] in the United Kingdom.

Swift, a medium-class Explorer mission was built in collaboration with national laboratories and universities including the Los Alamos National Laboratory, Penn State University, Sonoma State University, the University of Leicester and University College London Mullard Space Science Laboratory.

The Particle Physics and Astronomy Research Council (PPARC) is the UK's strategic science investment agency. It funds research, education and public understanding in four areas of science - particle physics, astronomy, cosmology and space science.

PPARC is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), and the European Space Agency and the European Southern Observatory. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank observatory.


Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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