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New gamma-ray burst smashes cosmic distance record

Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes. In the explosion, two jets of very fast moving material are ejected, as depicted in this artist’s illustration. If a jet happens to be aimed at Earth, we see a brief but powerful gamma-ray burst. Credit: ESO/A. Roquette

New gamma-ray burst smashes cosmic distance record

Leicester researchers in international team that has discovered earliest star explosion

Issued on 28 April 2009

The NASA/STFC/ASI Swift satellite has found a gamma-ray burst from a star that died when the Universe was 640 million years old, or less than 5 percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen and gives astronomers an insight into the early Universe. The international team, led by UK and US astronomers announced the discovery today, 28th April 2009.

“This is the most remote gamma-ray burst ever detected, and also the most distant object ever discovered — by some way.” Said Nial Tanvir, of the University of Leicester.

Dr Andrew Levan, University of Warwick said “At its most basic level this discovery tells us that there were massive stars at this moment in cosmic history, but equally importantly we can use events like this to probe how the universe evolves when it is less than 5 percent of its current age."

"The burst most likely arose from the explosion of a massive star," said Derek Fox at Penn State University, USA. "We're seeing the demise of a star – and probably the birth of a black hole – in one of the Universe's earliest stellar generations."

"Swift was designed to catch these very distant bursts," said Swift lead scientist Neil Gehrels at NASA's Goddard Space Flight Center.

At 3:55 a.m. EDT on 23rd April 2009 (08.55am BST), Swift satellite detected a ten-second-long gamma-ray burst of modest brightness. It quickly pivoted to bring its Ultraviolet/Optical and X-Ray telescopes to bear on the burst location. Swift saw a fading afterglow in X-rays but no corresponding glow in visible light.

"That alone suggested this was a very distant object," explained Fox. Beyond a certain distance, the expansion of the universe shifts all optical emission into longer infrared wavelengths. While a star's ultraviolet light could be similarly shifted into the visible region, UV-absorbing hydrogen gas grows thicker at earlier times. "If you look far enough away, you can't see visible light from any object," he noted.

Twenty minutes after the burst, Tanvir and his colleagues detected an infrared source at the Swift position using the STFC’s United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, Hawaii. "Burst afterglows provide us with the most information about the exploded star and its environs," Tanvir said. "But we have to target afterglows quickly because they fade out so fast."

An automated software system called eSTAR (run by University of Exeter astronomers Alasdair Allan and Tim Naylor), links telescopes from around the world. It picked up the gamma-ray burst alert and calculated that UKIRT could observe the right spot in the sky, and sent the telescope detailed instructions as to what was required.

The Director of UKIRT, Professor Gary Davis, said “We have worked hard to implement a rapid-response system for events just such as this. It is rewarding to see it used so spectacularly.”

Shortly after, Fox led an effort to obtain infrared images of the afterglow using the Gemini North Telescope on Mauna Kea. The source appeared in longer-wavelength images, but was absent in an image taken at the shortest wavelength (1 micron). The drop-out corresponded to a burst distance of about 13 billion light-years.

As Fox spread the word about the record distance, telescopes around the world slewed toward GRB 090423 to observe the afterglow before it faded away.

Follow up observations made by two teams reached the same conclusion, using different observatories – the burst was a record-breaker! At the Galileo National Telescope on La Palma in the Canary Islands, a team including Guido Chincarini at the University of Milan-Bicocca, Italy, determined that the afterglow's so-called redshift was 8.2. Tanvir's team measured the same redshift of 8.2 which equates to looking back 13 billion years in time, using the European Southern Observatory’s Very Large Telescope (VLT) on Cerro Paranal in Chile.

Gamma-ray bursts are the Universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets -- driven by processes not fully understood -- punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in other wavelengths.

The previous record holder was a burst with a redshift of 6.7, which places it 180 million light-years closer than GRB 090423.

The UK researchers are supported by the Science and Technology Facilities Council (STFC) which also funds the UK contribution to Swift, subscriptions to ESO and Gemini and owns the UK Infrared Telescope (UKIRT). Key parts of the instrumentation on Swift were built at the University of Leicester and University College London's Mullard Space Science Laboratory. Leicester also houses the UK Swift Science Data Centre which provided the most accurate X-ray location for GRB090423

Click here to view the NASA press release for this story.

Notes for Editors

Images

Available from the press office (Julia.maddock@stfc.ac.uk ) and http://www.stfc.ac.uk once the embargo expires.

Captions:

Artist’s impression of a gamma-ray burst

Gamma-ray bursts (GRBs) are short flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes. In the explosion, two jets of very fast moving material are ejected, as depicted in this artist’s illustration. If a jet happens to be aimed at Earth, we see a brief but powerful gamma-ray burst. Credit: ESO/A. Roquette

IR_afterglow_annotated.jpg and IR_afterglow.jpg

The fading infrared afterglow of GRB 090423 appears in the centre of this false-colour image taken with the Gemini North Telescope in Hawaii. The burst is the farthest cosmic explosion yet seen. Credit: Gemini Observatory/NSF/AURA , D. Fox and A. Cucchiara (Penn State Univ.) and E. Berger (Harvard Univ.)

GRB090423_Swift.jpg

This image merges data from Swift's Ultraviolet/Optical (blue, green) and X-Ray (orange, red) telescopes. No visible light accompanied the burst, which hints at great distance. The image is 6.3 arcminutes wide. Credit: NASA/Swift/Stefan Immler

Animation:

Gamma-ray bursts longer than two seconds are caused by the detonation of a massive star at the end of its life. Jets of particles and gamma radiation are emitted in opposite directions from the stellar core as the star collapses. This animation shows what a gamma-ray burst might look like up close. Credit: NASA/Swift/Cruz deWilde

http://svs.gsfc.nasa.gov/vis/a010000/a010300/a010369/index.html

Contacts

Professor Nial Tanvir

University of Leicester

Tel +46 46 222 1616 (land line whilst overseas)

Email nrt3@star.le.ac.uk

Dr Andrew Levan

University of Warwick

Email a.j.levan@warwick.ac.uk

Professor Paul O'Brien (available for interview)

University of Leicester

Office: +44 116 252 5203

E-mail: pto@star.le.ac.uk

Dr Mat Page (available for interview)

UCL Mullard Space Science Lab

Tel +44 1483 204283

mjp@mssl.ucl.ac.uk

Prof. Tim Naylor (available for interview)

Head of Physics

University of Exeter,

Tel +44 1392 264172

timn@astro.ex.ac.uk

Julia Maddock

Media Relations Manager

STFC

Tel +44 1793 442094

Julia.maddock@stfc.ac.uk

J.D. Harrington

NASA

Headquarters, Washington

Tel +1 202-358-5241

j.d.harrington@nasa.gov

Lynn Cominsky

Sonoma State University, Rohnert Park, Calif.

Tel +1 707-664-2655

lynnc@universe.sonoma.edu

Swift

Swift is managed by Goddard. It was built and is being operated in collaboration with Penn State University, University Park, Pa., the Los Alamos National Laboratory in New Mexico, and General Dynamics of Gilbert, Ariz., in the U.S. International collaborators include the University of Leicester and University College London’s Mullard Space Science Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, and additional partners in Germany and Japan. http://www.swift.ac.uk/

UKIRT

The world's largest telescope dedicated solely to infrared astronomy, the 3.8-metre (12.5-foot) UK Infrared Telescope (UKIRT) is sited near the summit of Mauna Kea, Hawaii, at an altitude of 4194 metres (13760 feet) above sea level. It is operated by the Joint Astronomy Centre in Hilo, Hawaii, on behalf of the UK Science and Technology Facilities Council. UKIRT's technical innovation and privileged position on the high, dry Mauna Kea site have placed it at the forefront of infrared astronomy since its opening in 1979. UKIRT is currently engaged in a world-leading infrared sky survey as well as the type of innovative individual programmes described in this press release. More about the UK Infrared Telescope: http://outreach.jach.hawaii.edu/articles/aboutukirt/

ESO’s Very Large Telescope Array

ESO operates three unique world-class observing sites in the Atacama Desert region of Chile: La Silla, Paranal and Chajnantor. ESO's first site is at La Silla, a 2400 m high mountain 600 km north of Santiago de Chile. It is equipped with several optical telescopes with mirror diameters of up to 3.6 metres. The 3.5-metre New Technology Telescope broke new ground for telescope engineering and design and was the first in the world to have a computer-controlled main mirror, a technology developed at ESO and now applied to most of the world's current large telescopes. While La Silla remains at the forefront of astronomy, and is still the second most scientifically productive in ground-based astronomy, the 2600 m high Paranal site with the Very Large Tele-scope array (VLT) is the flagship facility of European astronomy. Paranal is situated about 130 km south of Antofagasta in Chile, 12 km inland from the Pacific coast in one of the driest areas in the world. Scientific operations began in 1999 and have resulted in many extremely successful research programmes. http://www.eso.org

Science and Technology Facilities Council

The Science and Technology Facilities Council ensures the UK retains its leading place on the world stage by delivering world-class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange partnerships. The Council has a programme of public engagement to inspire students, teachers and the public with UK science.

The Council has a broad science portfolio including Astronomy, Particle Physics, Particle Astrophysics, Nuclear Physics, Space Science, Synchrotron Radiation, Neutron Sources and High Power Lasers. In addition the Council manages and operates three internationally renowned laboratories:

• The Rutherford Appleton Laboratory, Oxfordshire

• The Daresbury Laboratory, Cheshire

• The UK Astronomy Technology Centre, Edinburgh

The Council gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Laboratory for Particle Physics (CERN), the Institute Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF), the European organisation for Astronomical Research in the Southern Hemisphere (ESO) and the European Space Agency (ESA). It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank Observatory.

The Council is a partner in the UK space programme, coordinated by the British National Space Centre.

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