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).
Artist’s impression of a gamma-ray burst
Credit: ESO/A. Roquette
"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.
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 Centre. "We've waited five years, and we finally have one."
At 08.55am BST on 23rd April 2009 (03:55am EDT), 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."
Distribution redshifts
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 (European Southern Observatory) 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.
Notes for Editors
Images and captions
Image 1 - 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
Image 2 and Image 3 - 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.)
Image 4 - 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 1 (link opens in a new window) - 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
Contacts
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Professor Nial Tanvir
University of Leicester
Tel: +46 46 222 1616 (land line whilst overseas)
Mob: +44 (0)7980 136 499
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Dr Andrew Levan
University of Warwick
Mob: +44 (0)771 4250 373
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Prof Paul O'Brien (available for interview)
University of Leicester
Tel: +44 (0)116 252 5203
Mob: +44 (0)7891 894 071
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Dr Mat Page (available for interview)
University College London
Mullard Space Science Laboratory
Tel: +44 (0)1483 204 283
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Julia Maddock
Media Relations Manager
STFC
Tel: +44 (0)1793 442 094
Mob: +44 (0)7901 514 975
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J D Harrington
NASA Headquarters
Washington
Tel: +1 202 358 5241
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Lynn Cominsky
Sonoma State University
California
Tel: +1 707 664 2655
The eSTAR project
The eSTAR Project is a programme to build an intelligent robotic telescope network. It is a joint project between the Astrophysics Research Institute at Liverpool John Moores University and the Astrophysics Research Group of the School of Physics at the University of Exeter.
In collaboration with the Joint Astronomy Centre in Hawaii, and the Robonet-1.0 Project in the United Kingdom, the system is now operational performing rapid followup of Gamma-Ray Bursts on the 3.8m United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, and hunting for exo-planets using the Liverpool Telescope (LT) in La Palma, the Faulkes Telescope North (FTN) on Maui and the Faulkes Telescope South(FTS) in Siding Spring.
Swift
Swift (link opens in a new window) 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.
UKIRT
The world's largest telescope dedicated solely to infrared astronomy, the 3.8-metre (12.5-foot) UK Infrared Telescope (link opens in a new window) (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.
ESO's Very Large Telescope Array
ESO (link opens in a new window) operates three unique world-class observing sites in the Atacama Desert region of Chile: La Silla (link opens in a new window), Paranal (link opens in a new window) 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.
About STFC
Page last updated: 28 April 2009
by Julia Maddock
