Mullard Space Science Laboratory

P R E S S  R E L E A S E

01 February 2005
REF: SWIFT2005-1


The third telescope aboard NASA’s Swift gamma-ray observatory, the Ultraviolet/Optical Telescope (UVOT) with key involvement from UK scientists at University College London’s Mullard Space Science Laboratory, has seen first light and is now poised to observe its first gamma-ray burst. The UVOT captured an image of the Pinwheel Galaxy, known by amateur astronomers as the ‘perfect’ face-on spiral galaxy. With the UVOT turned on the Swift observatory is fully operational.  Swift's two other instruments - the Burst Alert Telescope (BAT) and the X-ray Telescope (XRT) with University of Leicester involvement - were turned on over the last few weeks and have been snapping up gamma-ray bursts ever since.

Swift is a NASA-led mission dedicated to unravelling the mysteries of gamma-ray bursts - random and fleeting explosions that signal the likely birth of black holes. 

"This was a real treat to point the UVOT toward the famous Pinwheel Galaxy, M101," said Dr. Peter Roming, UVOT Lead Scientist at the US Penn State University.  "The ultraviolet wavelengths in particular reveal regions of star formation in the galaxy’s spiral arms. But more than a pretty image, this first-light observation is a test of the UVOT's capabilities."

Swift's three telescopes work in unison. The BAT instrument detects gamma-ray bursts and autonomously turns the satellite in seconds to bring the burst within view of the XRT and the UVOT, which provide detailed follow-up observations of the burst afterglow.  Although the burst itself is gone within seconds, scientists can study the afterglow for clues about the origin and nature of the burst, much like detectives at a crime scene.

The UVOT serves several important functions.  First, it will pinpoint the gamma-ray burst location a few minutes after the BAT detection. The XRT provides a burst position within a 1- to 2-arcsecond range. The UVOT will provide sub-arcsecond precision, a spot on the sky about as wide as the eye of a needle at arm's length.  This information is then relayed to scientists at observatories around the world so that they can view the afterglow with other telescopes.

As the name implies, the UVOT captures the optical and ultraviolet component of the fading burst afterglow. Prof. Keith Mason, the UK UVOT lead at University College London’s Mullard Space Science Laboratory explains, “The 'big gun' optical observatories such as Hubble and Keck have provided useful data over the years, but only for the later portion of the afterglow. The UVOT isn't as powerful as these observatories, but has the advantage of observing from the very dark skies of space. Moreover it will start observing the burst afterglow within minutes, as opposed to the day or weeklong delay inherent with heavily used observatories. This is extremely important because the bulk of the afterglow fades within hours."

The ultraviolet portion will be particularly revealing, says Roming. "We know nearly nothing about the ultraviolet part of a gamma-ray burst afterglow," he said.  "This is because the atmosphere blocks most ultraviolet rays from reaching telescopes on Earth, and there have been few ultraviolet telescopes in orbit.  We simply haven't yet reached a burst fast enough with an ultraviolet telescope."

The UVOT's imaging capability will enable scientists to understand the shape of the afterglow as it evolves and fades.  The telescope's spectral capability will enable detailed analysis of the dynamics of the afterglow, such as the temperature, velocity and direction of material ejected in the explosion.

The UVOT will also help scientists determine the distance to the closer gamma-ray bursts, within a redshift of 4, which corresponds to a distance of about 12 billion light years. The XRT will determine distances to more distant bursts. 

Scientists hope to use the UVOT and XRT to observe the afterglow of short bursts, less than two seconds long.  Such afterglows have not yet been seen; it is not clear if they fade fast or simply don't exist. Some scientists think there are at least two kinds of gamma-ray bursts: longer ones (more than two seconds) that generate afterglows and that seem to be caused by massive star explosions; and shorter ones that may be caused by mergers of black holes or neutron stars. The UVOT and XRT will help rule out various theories and scenarios.

The UVOT is a 30-centimeter telescope with intensified CCD detectors and is nearly identical to an instrument on the European Space Agency's XMM-Newton mission. The UVOT is as sensitive as a four-meter optical ground-based telescope.  The UVOT's day-to-day observations, however, will look nothing like the Pinwheel Galaxy.  Distant and faint gamma-ray burst afterglows will appear as tiny smudges of light even to the powerful UVOT.  The UVOT is a joint product of Penn State and the Mullard Space Science Laboratory.


The UVOT first-light image is available on the Internet at and


M101 is a bright, face-on, spiral galaxy located in the constellation Ursa Major (containing the Big Dipper, also known as the Plough), about 15 million light years from Earth. These first light images of the M101 galaxy demonstrate that the UVOT is functioning well in detecting ultraviolet and optical data.  The UVOT is now poised on the Swift observatory to add to the limited data now available in optical wavelengths and to capture the first data ever available in ultraviolet wavelengths from an early gamma-ray-burst light curve.

Caption for Combined Ultraviolet-Optical Image (m101_combined.jpg)

This UVOT image combines both ultraviolet and visible light from a number of filters.  Each filter is sensitive to light of a different colour, ranging from ultraviolet light beyond the range of human eyesight through the blue to yellow portion of the visible spectrum. This is a ‘false-colour’ image with the shortest wavelength ultraviolet rays being represented as blue, and the longest visible light wavelengths as red. The image shows that hot young stars are being formed in abundance in M101, especially in the spiral arms of the galaxy, where they show up in ultraviolet light. The central regions of the galaxy have more cool, old stars, which appear ‘red’ in the picture. A number of foreground stars, located in our own Galaxy, also reveal themselves by their red colour.

Caption for Ultraviolet image (m101_uv.jpg)

This UVOT image of the pinwheel galaxy M101 is a 'false-colour' image generated with the UVOT ultraviolet filters.  Light from the shortest wavelength ultraviolet filter is represented by blue, with light from the next two shortest wavelength ultraviolet filters being represented by green and red, respectively. This image highlights the star forming regions in the spiral arms, where hot young stars are emitting mostly ultraviolet light.

Caption for Visible light image (m101_op.jpg)

This UVOT image of the pinwheel galaxy M101 is a 'false-colour' image generated with the near-UV,  the blue, and yellow filters, represented by blue, green, and red, respectively. This image shows more light from the central regions of the galaxy, where older, cooler stars dominate the emission.

Further information can also be found at:-

Background Notes

Swift is a medium-class explorer mission managed by NASA Goddard. This is a NASA mission with participation of the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom.  It was built in collaboration with national laboratories, universities and international partners, including Penn State University in Pennsylvania U.S.A.; Los Alamos National Laboratory in New Mexico U.S.A.; Sonoma State University in California U.S.A.; the University of Leicester in Leicester, UK; the Mullard Space Science Laboratory in Dorking, Surrey, UK; the Brera Observatory of the University of Milan in Italy; and the ASI Science Data Centre in Rome, Italy.

UK Role in Swift

The UK role in Swift has been to provide core elements of the narrow field instruments (the X-ray telescope and the UV/Optical telescope), utilising mature technology already developed for the ESA XMM-Newton mission, and the JeT-X instrument.

Mullard Space Science Laboratory, UCL

The major part of the UV/Optical telescope was constructed at MSSL using designs and expertise from the XMM-Newton Optical Monitor.

University of Leicester

Lead role in the X-ray telescope design, focal plane camera assembly and X-ray design (using past experience from JET-X and XMM-Newton). The UK SWIFT Science DATA Centre, at Leicester, will provide an archive of all SWIFT data, with open access for the wider UK astronomical community.

Science Contacts

Professor Keith Mason (Not available by phone on Feb 1st)

Mullard Space Science Laboratory

Tel: 01483 204100 (Switchboard)


Alex Blustin

Mullard Space Science Laboratory

Tel 01483 204196


Dr Peter Roming,

Penn State University

Tel: 00 1 814-865-7745

PR Contacts

Peter Barratt - PPARC Press Office

Tel: 01793 442012. Mobile: 0787 9602899


Gill Ormrod - PPARC Press Office

Tel: 01793 442012. Mobile: 0781 8013509


Lynn Cominsky (Swift PIO):

Email: Tel: (+1) 707-664-2655

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.