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: email@example.com 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: firstname.lastname@example.org 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: email@example.com Gill Ormrod PPARC Press Office Tel: 01793 442012 Fax: 01793 442002 Email: firstname.lastname@example.org 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 email@example.com 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.