100 Photographs in the Blink of an Eye
 
Scientists from the Universities of Sheffield and Southampton in
collaboration with the UK Astronomy Technology Centre at the Royal
Observatory, Edinburgh have just opened a new window on the Universe by
commissioning ULTRACAM - an ultra-fast camera which can take up to 1000
pictures a second in three different colours simultaneously.  The camera,
which is mounted on the largest optical telescope in Europe - the 4.2-m
William Herschel Telescope on La Palma in the Canary Islands - has been
designed to study some of the most rapid astronomical events.
 
Many people think of the sky as unchanging, so it may come as a surprise
that astronomers wish to take pictures so quickly. In fact, high speed
imaging is  essential to study some of the  most extreme astronomical
sources in the Universe, including black holes,  neutron stars and white
dwarfs.  These small but dense objects, representing the evolutionary
end-points of the lives of stars, typically pack a few times the mass of
the Sun into a volume only a few kilometres across.  Their precise masses
and sizes are not well known and very difficult to determine, but such
information is crucial if we are to understand how stars age and die. In
principle, it is possible to determine these parameters by observing
eclipsing binary star systems, in which the black hole, neutron star or
white dwarf sucks material from a larger companion star in orbit around
it.  The problem is that material in orbit close to the surface of a
black hole or neutron star completes one orbit in about a millisecond (or
about a second if the object is a white dwarf).
 
This is where ULTRACAM excels. By taking up to 1000 images a second in
three different colours simultaneously, astronomers will now be able to
study material in the innermost orbits around black holes, neutron stars
and white dwarfs and observe how the light from these objects varies as
the companion star obscures our line of sight to them. This allows a
direct measurement of their masses, sizes and temperatures, enabling
astronomers to test the fundamental physics which describes the extreme
state of matter of which black holes,  neutron stars and white dwarfs are
made.
 
Dr Vik Dhillon, the ULTRACAM project scientist, remarks: "For the first
time, astronomers have an instrument specifically designed for the study
of high-speed astrophysics. Using ULTRACAM in conjunction with the
current generation of large telescopes means that it is now possible to
study high-speed celestial phenomena such as eclipses, oscillations and
occultations in stars which are millions of times too faint to see with
the naked eye."
 
ULTRACAM employs the latest in CCD detector technology in order to take, 
store and analyse data at the required sensitivities and speeds. CCD
detectors can be found in digital cameras and camcorders, but the devices
used in ULTRACAM are special because they are larger, faster and most
importantly, much more sensitive to light than the detectors used in
today's consumer electronics products. Work started on the instrument
during the summer of 1999, when the  project was awarded  300,000 of
funding by the UK's  Particle Physics and Astronomy Research Council. The
project was completed on-budget and ahead of schedule in May 2002, when
the instrument saw "first light" on the 4.2-m William Herschel Telescope
on La Palma. As well as successfully commissioning the instrument, the
project team also acquired the first scientific data on white dwarf
stars, showing that the instrument is working to specification. The
project team expect to obtain the first scientific results on the more
demanding neutron stars and black holes during a second visit to the
telescope in September 2002.
 

Contacts
 
Dr Vik Dhillon
Department of Physics and Astronomy
University of Sheffield
Sheffield S3 7RH
United Kingdom
tel: +44-114-222-4528
fax: +44-114-272-8079
email: vik.dhillon@sheffield.ac.uk
 
Dr Tom Marsh
Department of Physics and Astronomy
Southampton University
Highfield
Southampton S017 1BJ
United Kingdom
tel: +44-23-8059-2063
fax: +44-23-8059-3910
email: trm@astro.soton.ac.uk
 
Mr Andy Vick
UK Astronomy Technology Centre
Royal Observatory, Edinburgh
Blackford Hill
Edinburgh EH9 3HJ
United Kingdom
tel: +44-131-668-8310
fax: +44-131-668-8264
email: ajv@roe.ac.uk
 
Gill Ormrod
PPARC Press Office
Tel: 01793 442012
Fax: 01793 442002
Email: gill.ormrod@pparc.ac.uk
 
Images and further information
 
Project web pages can be found at:
http://www.shef.ac.uk/~phys/people/vdhillon/ultracam
 
The following images are available from the PPARC website www.pparc.ac.uk
or from Gill Ormrod at PPARC on 01793 442012 or email
gill.ormrod@pparc.ac.uk
 
Close-up photograph of ULTRACAM mounted at the Cassegrain focus of the
4.2-m William Herschel Telescope on La Palma.
 
An artist's impression of an X-ray binary star, consisting of a black
hole (which lies at the heart of the accretion disc, at the point where
the jets originate) pulling material from a solar-like companion star.
This type of object will be one of the main targets for study with
ULTRACAM. Picture courtesy
of Dr Rob Hynes (University of Southampton).
 

The following ULTRACAM first-light images are available from
http://www.shef.ac.uk/~phys/people/pkerry/ultracam.html
 
- the globular cluster M13 in the constellation Hercules
- spiral galaxy M51 in the constellation Canes Venatici (the Hunting
Dogs).
 
Notes for editors
 
1. 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 broad 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, 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.
 
2. The UK Astronomy Technology Centre is located at the Royal
Observatory, Edinburgh (ROE). It is a scientific site belonging to the
Particle Physics and Astronomy Research Council (PPARC). The mission of
the UK ATC is to support the mission and strategic aims of PPARC and to
help keep the UK at the forefront of world astronomy by providing a UK
focus for the design, production and promotion of state of the art
astronomical technology. The Royal Observatory, Edinburgh comprises the
UK Astronomy Technology Centre (UK ATC) of the Particle Physics and
Astronomy Research Council (PPARC), the Institute for Astronomy (IfA) of
the University of Edinburgh and the ROE Visitor Centre.
 

3. The 4.2-m William Herschel Telescope (WHT) is operated on the
island of La Palma in the Canary Islands in Spain by the UK's Particle
Physics and Astronomy Research Council, its Dutch equivalent, the NWO and
the Spanish Instituto de Astrofisica de Canarias (IAC).
 
4. White dwarf: A late stage of stellar evolution for stars of up to
about 1.5 times the mass of the Sun. A white dwarf is formed when such a
star exhausts its sources of fuel for nuclear fusion and collapses under
its own gravity to a highly compressed and very dense state. Stars of
greater mass become even denser neutron stars or black holes. White
dwarfs have no internal source of energy and so gradually cool into dead,
inactive stellar relics called black dwarfs.
 
5. Neutron star: A compact, extremely dense star composed almost entirely
of neutrons. They are formed when stars between about 1.5 and 3 times the
mass of the Sun run out of nuclear fuel, explode as a supernova and then
collapse under their own gravity to a very dense state in which protons
and electrons fuse to form neutrons. More massive stars collapse even
further and become black holes. Less massive stars collapse to become
white dwarf stars.
 
6. Black hole: A region of space surrounding an extremely dense
concentration of matter, in which the gravitational force is so strong
that matter and energy cannot escape from it.
 
7. Why does ULTRACAM produce photographs in 3 colours simultaneously?
The reason is that the material at different temperatures will emit
radiation in different colours, and hence by observing the variability in
the 3 colours simultaneously different regions of the object can be
probed (this also gives a crude idea of their temperature). The 3 colours
have to be simultaneous as if taken sequentially there is the problem of
the object varying between the exposures of the different colours.