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Cymraeg

Cardiff astronomers help create the largest sub-millimetre camera

06 December 2011

Cardiff - Scuba WebA composite image of the Whirlpool Galaxy as seen by SCUBA-2 (red and blue) and the Hubble Space Telescope (green). The cold dust that SCUBA-2 detects marks the locations that stars are forming, which are generally dark when seen in visible light. These star-forming regions trace the spiral arms, with one stretching up to the nearby companion galaxy seen at the top of the image. The cold dust marks places The Whirlpool Galaxy is located 31 million light years from Earth in the constellation of Canes Venatici. Image credit: JAC/UBC (SCUBA-2), NASA (Hubble)

SCUBA-2 is far more sensitive and powerful than previous instruments with more than 10,000 pixels it is the largest camera of its type ever built and will help revolutionise the field of sub-millimetre astronomy. Using its images, astronomers will now be able to see some of the coldest material in the Universe.

SCUBA-2 is mounted on the 15-metre diameter James Clerk Maxwell Telescope, which is near the summit of Mauna Kea in Hawaii. Its location at a high altitude of 4100m (14000ft) puts the telescope, the largest of its kind in the world, above a large fraction of the atmosphere – which would otherwise absorb much of the sub-millimetre light it is trying to detect.

"When you look up at the stars, you only see the light they are emitting in the visible part of the spectrum" explained Professor Gary Davis, Director of the JCMT and a visiting professor at Cardiff University.

"Many galaxies, including our own Milky Way, contain huge amounts of cold dust that absorbs visible light and these dusty regions just look black when seen through an optical telescope. The absorbed energy is then re-radiated by the dust at longer, sub-millimetre, wavelengths," he added.

The development of SCUBA-2 involved many teams from the UK and around the world. It is technically very complex, not least because the detectors have to be cooled to a tenth of a degree above absolute zero – making it one of the coldest places in the known Universe.

Cardiff University’s School of Physics and Astronomy provided the cold cryogenic structures and performed laboratory testing of the detector arrays.

"The SCUBA-2 superconducting detector arrays are cooled to such low temperatures in order to provide ultra high sensitivity along with unprecedented imaging capabilities. Although used here for the detection of sub-millimetre emission from the cosmos this technology is creating exciting possibilities for its use at other wavelengths", said Professor Peter Ade, who led the Cardiff involvement.

Cardiff - Scuba 2 WebSCUBA-2 mounted on the back of the James Clerk Maxwell Telescope. Image credit: JAC

"SCUBA-2 is already providing detailed images of nearby star forming regions and detecting galaxies at the edge of the observable universe and will maintain the UKs leading role in this area of astronomical research," he added.

UK, Canadian and Dutch researchers have pioneered observations of the sky in the sub-millimetre wavelength range through their partnership on the James Clerk Maxwell Telescope. SCUBA-2’s predecessor, SCUBA, produced many new and unexpected discoveries, from a previously unknown population of distant, dusty galaxies (known ever since as ‘SCUBA galaxies’), to the first images of cold debris discs around nearby stars, which may indicate the presence of planetary systems.

Observing in these long wavelengths allows astronomers to see some of the coldest material in the Universe – gas and dust that is only around 10 degrees above absolute zero, or -263 Celsius.

Professor Derek Ward Thompson, who studies the formation of stars, said "Stars are born inside dense clouds of very cold material, and we will now be able to study these in more detail and much faster than ever before. Judging by these first observations, SCUBA-2 will provide a huge leap forward in our understanding of the processes involved in star formation."

As well as looking at stars forming in our own galaxy, SCUBA-2 will be used to study other galaxies. But it won’t be limited to our own Galactic neighbourhood, and will allow astronomers to pick out individual galaxies that formed when the Universe was just a fraction of its current age.

"Mapping the distribution of these galaxies over huge areas of the sky is one of the best ways of studying how the Universe behaves on the largest scales", commented Professor Steve Eales of Cardiff University. "While SCUBA took 20 nights to map an area the size of the full Moon, SCUBA-2 will cover the same area in a couple of hours".

SCUBA-2 will provide a new and precise understanding of star formation throughout the history of the Universe. Cardiff’s Professor Matt Griffin is on the JCMT Board, and commented: "The SCUBA camera was one of the most successful astronomical instruments in recent decades, and SCUBA-2 will certainly improve on that. We are delighted that SCUBA-2 is now open for business."

Cardiff Involvement in SCUBA-2

Cardiff University provided the cold cryogenic structures used in the instrument, and conducted laboratory testing of the detectors before shipping them to Hawaii. Cardiff researchers have also been involved in the testing and commissioning of the instrument on site at the JCMT.

Further information/media interviews:

Professor Peter Ade

School of Physics and Astronomy

Cardiff University

Email: peter.ade [@] astro.cf.ac.uk

Tel: +44 (0)29 20 874 643

Professor Derek Ward-Thompson

School of Physics and Astronomy

Cardiff University

Email: Derek.ward-thompson [@] astro.cf.ac.uk

Tel: +44 (0)29 20 875 314

Professor Steve Eales

School of Physics and Astronomy

Cardiff University

Email: steve.eales [@] astro.cf.ac.uk

Tel: +44 (0)29 20 876 168

Professor Matt Griffin

School of Physics and Astronomy

Cardiff University

Email: matt.griffin [@] astro.cf.ac.uk

Tel: +44 (0)29 20 874 203

Professor Gary Davis

JCMT director

Joint Astronomy Centre, Hawaii

Email: g.davis@jach.hawaii.edu

Tel: +1 808-969-6504

Dr Chris North

School of Physics and Astronomy

Cardiff University

Email: chris.north@astro.cf.ac.uk

Tel: +44 (0)29 20 870 537

SCUBA-2 key facts

· Size: 3m (height), 2.4m (width), 2.6m (depth)

· Weight: 4.5 tonnes (about three times the weight of a typical car)

· Temperature of detectors: 0.1K = –272.9°C = –459.2°F

· Submillimetre camera with 5120 pixels (4 sub arrays x 1280 pixels) at each wavelength band

· Provides a unique wide-field submillimetre imaging capability at 450 and 850 microns

· Hundreds of times faster at mapping large areas of sky than predecessor SCUBA to the same signal-to-noise

· Uses superconducting transition edge sensors as the light-sensitive elements

· Addresses a wide-range of scientific issues including how galaxies, stars and planets form

· Acts as a wide-field "pathfinder" for the new generation of submillimetre interferometers (e.g. SMA and ALMA)

The SCUBA-2 project is a collaboration of several observatories or laboratories. The project was led by the UK Astronomy Technology Centre (UK ATC) with the partners:

· University of Edinburgh (array structures)

· Cardiff University (Focal Plane Units and 1K enclosure)

· US National Institute of Standards and Technology (detector arrays and readout)

· University of British Columbia, Canada (multi-channel electronics and data reduction software)

· University of Waterloo, Canada (multiplexer screening)

· Joint Astronomy Centre (infrastructure and software).

A 2001 survey by the US-based Space Telescope Science Institute revealed that scientific results from SCUBA-2’s predecessor, SCUBA had been cited almost as often as those from the Hubble Space Telescope, and much more so than those from any other ground-based facility or satellite project. The project was funded by the Science and Technology Facilities Council (STFC), the JAC, and the Canada Foundation for Innovation.

For more information on SCUBA-2 visit: www.roe.ac.uk/ukatc/projects/scubatwo/