Astronomy in the fast lane!

UK scientists have opened a new window on the Universe with the recent commissioning of ULTRACAM on the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Chile. This ultra fast camera is capable of capturing some of the most rapid astronomical events in the cosmos.

ULTRACAM, the first UK-built instrument to be mounted on the VLT, has been designed and built by scientists from the Universities of Sheffield and Warwick, in collaboration with the UK Astronomy Technology Centre in Edinburgh. It can take up to 500 pictures a second in three different colours simultaneously.

ULTRACAM employs the latest in charged coupled device (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.

In May 2002 the ULTRACAM saw first light on the 4.2-m William Herschel Telescope (WHT) on La Palma where it captured a variety of cosmic events including eclipses, transits, flickers, flares, outbursts and explosions. These observations have produced a bonanza of new and exciting results, leading to 11 scientific papers being published or in press.

However, in order to study the very faintest stars at the very highest speeds, it is necessary to use one of the world's largest telescopes located at one of the world's best astronomical sites. With this in mind, work began 2 years ago preparing ULTRACAM for use on the VLT, situated in the Atacama Desert in Chile.

Dr Vik Dhillon, ULTRACAM project scientist from the University of Sheffield said, "Astronomers using the VLT now have an instrument specifically designed for the study of high-speed phenomena. 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." He adds, "ULTRACAM is leading the way in combining an innovative technology with one of the best astronomical facilities in the world."

The instrument saw first light on the VLT on May 4, 2005, and was then used for 17 consecutive nights on the telescope to study extrasolar planets, black-hole binary systems, pulsars, white dwarfs, asteroseismology, cataclysmic variables, brown dwarfs, gamma-ray bursts, active-galactic nuclei and Kuiper-belt objects. "These few nights with ULTRACAM on the VLT have demonstrated the unique discoveries that can be made by combining innovative technology with one of the best astronomical observatories in the world," said Tom Marsh, ULTRACAM team member from the University of Warwick. "We hope that ULTRACAM will now become a regular visitor at the VLT, giving European astronomers access to a unique tool with which to study the Universe."

ESO release


PR Contacts

Dr Henri Boffin - ESO Press Officer
European Southern Observatory (Garching)
Tel: +49-89-3200-6222. Email: hboffin@eso.org

Gill Ormrod - PPARC Press Office
Tel: +44 (0)1793 442012. Email: gill.ormrod@pparc.ac.uk

Lorna Branton MCIPR - University of Sheffield Press Office
Tel: 0114 222 1046.

Eleanor Gilchrist - ROE Press Office
Tel: +44 (0)131 6688397. Email: efg@roe.ac.uk

Science Contacts

Dr Vik Dhillon, Department of Physics and Astronomy
University of Sheffield
Tel: +44-114-222-4528. Email: vik.dhillon@sheffield.ac.uk

Professor Tom Marsh, Department of Physics
University of Warwick
Tel: +44-24765-74739. Email: t.r.marsh@warwick.ac.uk

Mr Andy Vick, UK Astronomy Technology Centre
Royal Observatory, Edinburgh
Tel: +44-131-668-8310. Email: ajv@roe.ac.uk

Dr Kieran O'Brien - European Southern Observatory (Chile)
Tel: +56-2-463-3107. Email: kobrien@eso.org


Images

ULTRACAM mounted on VLT

ULTRACAM mounted on the visitor focus of the VLT UT3 (Melipal).

Credit: ULTRACAM team

 

The commissioning team

The commissioning team in the VLT control room at first light. From left to right: Pascal Robert (ESO), Ariel Lopez (ESO), Kieran O'Brien (ESO), Andy Vick (UKATC), David Atkinson (UKATC), Paul Kerry (Sheffield), Vik Dhillon (Sheffield), Stuart Littlefair (Sheffield), Andreas Kaufer (ESO), Tom Marsh (Warwick).

Credit: ULTRACAM team

First light image

First light with ULTRACAM on the VLT: The field of the transitting extrasolar planet OGLE-TR-56b. The image shows only a portion of one of the three ULTRACAM CCD chips. Thousands of such 1 s images were obtained in order to derive an accurate light curve of the transit at three different wavelengths, thereby enabling an accurate determination the radius of the planet.

Credit: ULTRACAM team

Early scientific highlight

An early scientific highlight from the first few nights of the ULTRACAM run on the VLT: Light curves in i' (red) and g' (green) of the quiescent black-hole X-ray transient GU Mus. This object consists of a black hole in a 10-hour orbit with a normal solar-like star. The black hole is surrounded by an accretion disk of material transferred from the solar-like star. As this material accretes onto the black hole, energy is released, and this is evident from the large-amplitude flares visible in the light curve. What was not expected, however, is the series of sharp spikes that can be seen, which are separated by approximately 7 minutes. Such a stable signal must be tied to a relatively stable structure in the accretion disk, such as the proposed transition region between normal and advective flows within the disk. Note that GU Mus has magnitude of g' = 21.4 and we used an exposure time of only 5 seconds - such observations would have been impossible without the aperture and excellent observing conditions of the VLT.

Credit: ULTRACAM/VLT ESO

Artisit's illustration of X-ray binary star

An artist's illustration 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.

Picture courtesy of Professor Rob Hynes (Lousiana State University).


Websites

www.eso.org

ULTRACAM


ULTRACAM team

The ULTRACAM team is composed of Vik Dhillon, Stuart Littlefair and Paul Kerry (Sheffield, UK), Tom Marsh (Warwick, UK), Andy Vick and Dave Atkinson (UKATC, Edinburgh). For the installation on the VLT they received support from Kieran O'Brien

ULTRACAM is the first instrument to make use of the VLT 'visitor focus' - which allows innovative technologies and instrumentation to be added to the telescope for short periods of time, allowing studies to take place that are not available with the current suite of instruments.

Example science case in ULTRACAM's first run

One particular example of a science case in this run was the study of a light curve of an exoplanet. Of the 133 known extrasolar planets only 7 transit the face of their parent star. Five of the seven have been discovered by the Optical Gravitational Lensing Experiment (OGLE) on the VLT. ULTRACAM will be used on the VLT to obtain simultaneous, multi-colour light curves of four of the OGLE planets at millimeters magnitude precision and 4 second time resolution. This data will be used to measure accurate masses and radii for the OGLE planets. It will also be used to search for variations in planetary radius as a function of wavelength, allowing us to directly study the planetary atmospheres, as the planets appear slightly larger when observed at wavelengths where atmosphere contains strong opacity sources.

Background information

The European Southern Observatory is an intergovernmental, European organisation for astronomical research. It has eleven member countries. ESO operates astronomical observatories in Chile and has its headquarters in Garching, near Munich, Germany.

The ESO Very Large Telescope (VLT) at the Paranal Observatory (Atacama, Chile) is the world's largest and most advanced optical telescope. It comprises four 8.2-m reflecting Unit Telescopes and several moving 1.8-m Auxiliary Telescopes, the light beams of which can be combined in the VLT Interferometer (VLTI). With its unprecedented optical resolution and unsurpassed surface area, the VLT produces extremely sharp images and can record light from the faintest and most remote objects in the Universe.

The four large telescopes that make up the VLT are named ANTU (the Sun) , KUEYEN (the Moon), MELIPAL (the Southern Cross) and YEPUN (Venus). These four names are taken from the Mapuche (Mapudungun) language of the indigenous people that live in the area south of the Bio-Bio River, some 500 km south of Santiago de Chile.

The UK and ESO

The UK joined ESO in July 2002. In joining ESO, UK astronomers have gained access to the four 8.2-metre telescopes that comprise the Very Large Telescope (VLT) and to the several 1.8-metre telescopes that make up the Very Large Telescope Interferometer (VLTI); These facilities are located in the northern part of the Atacama desert in Chile. They also have access to two 4-metre class telescopes and several smaller ones at the ESO La Silla observatory further south in Chile.

The UK will benefit from increased involvement in the design, construction and scientific discoveries of the Atacama Large Millimetre Array (ALMA), a network of 64 twelve-metre radio telescopes also to be sited in Chile, and will have the opportunity to play a defining role in ESO's 100-metre Overwhelmingly Large (OWL) optical infrared telescope.

The 4-metre Visible and Infrared Survey Telescope (VISTA) forms part of the UK entry contribution to ESO. It is a specialised wide-angle facility equipped with a powerful camera of novel design and efficient detectors that will enable it to obtain deep images of large sky areas in short time. These survey observations will be made in several wavebands in the near-infrared region of the electromagnetic spectrum, with the capability of adding a visible region camera later. VISTA will be installed at the ESO Paranal Observatory (Chile).

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 Organisation for Nuclear Research, 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.