Robotic telescope unravels mystery of cosmic blasts (Forwarded)

Liverpool John Moores University
Liverpool, U.K.

16 March 2007

Robotic telescope unravels mystery of cosmic blasts

Liverpool Telescope is helping gather fundamental evidence on Gamma Ray
Bursts

Scientists have used the world's largest robotic telescope -- LJMU's
Liverpool Telescope -- to make the earliest-ever measurement of the
optical polarisation of a Gamma Ray Burst (GRB) just 203 seconds after the
start of the cosmic explosion. This finding, which provides new insight
into GRB physics, is published in Science today (15th March 2007).

The scientists from LJMU and colleagues in the UK, Italy, France and
Slovenia used the Liverpool Telescope on the island of La Palma and its
novel new polarimeter, RINGO, to perform the measurement following
detection of the burst by NASA's Swift satellite. The Liverpool Telescope
was designed and built by LJMU and is still onwed by the University.

Gamma Ray Bursts are the most instantaneously powerful explosions in the
Universe and are identified as brief, intense and completely unpredictable
flashes of high energy gamma rays on the sky. They are thought to be
produced by the death throes of a massive star and signal the birth of a
new black hole or neutron star (magnetar) and ejection of an ultra-high
speed jet of plasma. Until now, the composition of the ejected material
has remained a mystery and, in particular the importance of magnetic
fields has been hotly debated by GRB scientists.

The Liverpool measurement was obtained nearly 100 times faster than any
previously published optical polarisation measurement for a GRB afterglow
and answers some fundamental questions about the presence of magnetic
fields.

Principal author of the Science paper and GRB team leader Dr Carole
Mundell, who is based at LJMU's Astrophysics Research Institute, said:
"Our new measurements, made shortly after the Gamma Ray Burst, show that
the level of polarisation in the afterglow is very low. Combined with our
knowledge of how the light from this explosion faded, this rules-out the
presence of strong magnetic fields in the emitting material flowing out
from the explosion -- a key element of some theories of GRBs."

The so-called optical afterglow is thought to originate from light emitted
when this ejected material impacts the gas surrounding the star. In the
first few minutes after the initial burst of gamma rays, the optical light
carries important clues to the origin of these catastrophic explosions;
capturing this light at the earliest possible opportunity and measuring
its properties is ideally suited to the capabilities of large robotic
telescopes like the Liverpool Telescope.

Lord Martin Rees, Astronomer Royal and President of the Royal Society
said: "We are still flummoxed about the underlying 'trigger' for gamma ray
bursts, and why they sometimes emit bright flashes of light. Theorists
have a lot of tentative ideas, and these observations narrow down the
range of options."

Professor Keith Mason, CEO of the Particle Physics and Astronomy Council
(PPARC) and UK lead investigator on Swift's Ultra Violet/Optical
Telescope, said: "This result demonstrates well the effectiveness of
Swift's rapid response alert system, allowing robotic telescopes, such as
the Liverpool Telescope, to follow up gamma ray bursts within seconds,
furthering our knowledge with each detection."

For more information on LJMU's Liverpool Telescope, visit:
http://telescope.livjm.ac.uk/

For more information on the Swift satellite, visit:
http://www.nasa.gov/mission_pages/swift/main/index.html

Figure caption:
[http://telescope.livjm.ac.uk/pics/News/grb_fig1.gif (33KB)]

(1) Gamma Ray Burst, GRB 060418, explodes and emits high-energy gamma rays

(2) and (3) Swift satellite detects gamma rays and sends notification of
sky location to ground telescopes

(4) Liverpool Telescope (LT) on mountain top on Canary island of La Palma
receives notification and immediately points to correct part of sky to
begin to capture optical light from GRB afterglow.

(5) Polarisation image taken with LT polarimeter, RINGO, is transmitted to
the Astrophysics Institute at LJMU for analysis by scientists.

Credit: Dr Carole Mundell, Liverpool John Moores University.