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Planck space observatory unveils the coldest regions of our galaxy

17 March 2010

Planck images a galactic web of cold dust.
The image above covers a portion of the sky about 55 degrees across. It is a three-colour combination constructed from Planck's two shortest wavelength channels (540 and 350 micrometres, corresponding to frequencies of 545 and 857 GHz respectively), and an image at 100 micrometres obtained with the Infrared Astronomical Satellite (IRAS). This combination effectively traces the dust temperature: reddish tones correspond to temperatures as cold as 12 degrees above absolute zero, and whitish tones to significantly warmer ones (a few tens of degrees above absolute zero) in regions where massive stars are currently forming. Overall, the image shows local dust structures within 500 light years of the Sun.
This Planck image was obtained during the first Planck all-sky survey which began in mid-August 2009. By mid-March 2010 more than 98% of the sky had been observed by Planck. Because of the way Planck scans the sky 100% sky coverage for the first survey will take until late-May 2010.
Image Credit: ESA/HFI Consortium/IRAS

Giant filaments of cold dust stretching through the coldest regions of our Galaxy are revealed in new images, released today (17th March), from ESA's Planck satellite. Analysing these structures could help to determine the forces that shape our Galaxy and trigger star formation.

These images are a scientific by-product of a mission which will ultimately provide the best picture ever of the early Universe.

Vital components of the spacecraft were designed and built by staff at the University of Manchester's Jodrell Bank Centre for Astrophysics. The Manchester astronomers are now playing a major role in analysing the scientific data being produced.

Prof Richard Davis of the University of Manchester's Jodrell Bank Centre for Astrophysics says

"These are fantastically detailed images showing the sky at a wavelength never previously investigated. Our main aim with Planck is to observe the cosmic microwave background, the fading glow of the Big Bang. However the emissions from our own Galaxy, the so-called foregrounds, restrict our ability to do that. When these high-frequency images are combined with those from the low-frequency instrument, key components of which were built here at Jodrell Bank, we will be able to accurately separate the foreground. In addition to enabling extremely precise measurements of the microwave background, this will result in all sorts of new science on the physical processes at work in our Galaxy."

Dr Clive Dickinson, also of the University of Manchester, adds

"These new multi-frequency images from Planck will revolutionise our understanding of the radio and sub-mm sky. I'm amazed by the beautiful structures that they reveal. It is often difficult to make radio images showing such a wide range of scales and brightnesses, but these Planck results are as good as any I've seen from telescopes working in other parts of the spectrum."

Dr David Parker, Director of Space Science and Exploration at the British National Space Centre (BNSC), said,

"Less than a year since it was launched, Planck is producing some spectacular results. The Planck spacecraft is just one of a family of cutting edge scientific missions in which the UK is already playing a major role. I'm looking forward to fresh discoveries and continued involvement in such exciting missions with the forthcoming creation of a UK executive space agency."

ESA's Planck satellite - the first European mission designed to study the Cosmic Microwave Background (CMB) - has begun the second of four full-sky surveys, which will ultimately provide the most detailed information yet about the size, mass, age, geometry, composition and fate of the Universe. Although the primary goal of Planck is to map the CMB, by surveying the entire sky with an unprecedented combination of frequency coverage, angular resolution, and sensitivity, Planck will also provide valuable data for a broad range of studies in astrophysics. This is clearly demonstrated in the new images which trace the cold dust in our Galaxy and reveal the large-scale structure of the interstellar medium filling the Milky Way.

One of the key advantages of Planck is its ability to measure the temperature of the coldest dust particles and locate the coldest dusty clumps in the Galaxy, areas where star formation is about to occur. Figure 1 demonstrates how Planck measures this cold dust: reddish tones correspond to temperatures as cold as 12 degrees above absolute zero, and whitish tones to much warmer ones (a few tens of degrees) in regions where massive stars are currently forming. As the clumps shrink, they become denser and better at shielding their interiors from light and other radiation. This allows them to cool more easily and collapse faster. Planck excels at detecting these dusty clumps across the whole sky and contributes the crucial information required to measure accurately the temperature of dust at these large scales.

"What makes these structures have these particular shapes is not well understood," says Jan Tauber, ESA Project Scientist for Planck. The denser parts are called molecular clouds while the more diffuse parts are 'cirrus'. They consist of both dust and gas, although the gas does not show up directly in this image. There are many forces at work in the Galaxy to help shape the molecular clouds and cirrus into these filamentary patterns. For example, on large scales the Galaxy rotates, creating spiral patterns of stars, dust, and gas. Gravity exerts an important influence, pulling on the dust and gas. Radiation and particle jets from stars push the dust and gas around on smaller scales, and magnetic fields also play a role, although to what extent is presently unclear.

Planck and Herschel images
Filamentary structures are apparent at large-scales (as shown in this Planck image, on the right) and small-scales (as seen on the left, a Herschel image of a region in Aquila) in the Milky Way.
Image credit: ESA/HFI Consortium. Credits for inset: ESA/SPIRE and PACS consortia/P. Andre (CEA Saclay) for the Gould's Belt Key Programme Consortium

The space between stars is not empty but rather is filled with clouds of dust and gas, intimately mixed together and known as the 'interstellar medium'. The right hand image of figure 2, covers the same region as figure 1: about 55 degrees across and looking in the direction of the centre of our Galaxy. The plane of the Galaxy is seen as the horizontal band across the bottom of the image. Above the plane, the filamentary structure of the interstellar medium in the solar neighbourhood (within a few hundred light years of the Sun) can be seen.

The image on the left in figure 2 shows a typical 'stellar nursery' (about 3 degrees across) in the constellation of Aquila, recently imaged by the Herschel Space Observatory. The filamentary structures seen at the smallest scales by Herschel are strikingly similar in appearance to those seen at the largest scales by Planck.

The richness of the structure that is observed, and the way in which small and large scales are interconnected, provide important clues to the physical mechanisms underpinning the formation of stars and of galaxies. This example illustrates the synergy between Herschel and Planck; together these missions are imaging both the small-scale and the large-scale structure of our Galaxy.

Dr David Clements from Imperial College London, said,

"These wonderful new images from Planck clearly show its power for revealing new things about the universe. We always knew there would be a lot of great new science found as we peeled away the layers of the cosmic onion to reach the microwave background, and these results demonstrate that happening in our own galaxy. What I hadn't really grasped was just how beautiful the Planck foreground images were going to be!"

Tom Bradshaw from the Science and Technology Facilities Council's Rutherford Appleton Laboratory added,

"Planck is a satellite designed to measure the temperature of deep space to unprecedented accuracy. The technology to achieve this has been under development for over 15 years. A significant part of this was developed in the UK. After all the hard work that has been put into what is probably one of the most complex satellites ever flown, it is gratifying to see such stunning images that will help us understand our place in the universe."

Notes for Editors

The Planck satellite was launched along with the Herschel satellite on 14th May 2009 from Kourou, French Guiana, on an Ariane 5 rocket. During its 6 week journey to its observation point around Lagrange point 2, 1.5 million km (1 million miles) from Earth, the scientific instruments were cooled to extremely low temperatures, making Planck the coldest object in space at just 0.1° above absolute zero (-273.15°C). It took around 6 weeks for Planck to cool down to these low temperatures, after which a further 6 weeks were spent calibrating the instruments.

UK role in Planck

The UK is playing a major role in the Planck mission, with funding from the Science and Technology Facilities Council (STFC). The UK is the second largest financial contributor to the ESA Science Programme which builds and launches space missions such as Planck using leading-edge technology from the UK space industry. In addition, STFC has invested £17.4M to build instrumentation for Planck.

A number of UK institutes and companies form part of the consortium building the two focal plane instruments, HFI (High Frequency Instrument) and LFI (Low Frequency Instrument). The Jodrell Bank Observatory at The University of Manchester has produced critical elements of the LFI receiver modules. Cardiff University, STFC RAL and SEA have been involved with hardware development for HFI, while various UK research groups including Imperial College London and University of Cambridge form the London Planck Analysis Centre and Cambridge Planck Analysis Centre. These groups are involved with data analysis and simulation for the HFI data analysis and simulation software. More information can be found in the Planck briefing document.

Jodrell Bank's role in Planck

Jodrell Bank Centre for Astrophysics (JBCA) is directly involved with the two lowest frequencies of the Low Frequency Instrument, the 30 and 44 GHz radiometers. These have 4 and 6 detectors respectively, operating at 20K (-253.15°C or -423.67°F). The resolution on the sky will be 33 and 23 arc minutes, and the sensitivity 1.6 and 2.4 micro K (1s, over 12 months). The radiometers were built by a European collaboration: the cryogenic low noise amplifiers which are the heart of the radiometers were developed at Jodrell Bank, with help from the University of Birmingham and The Rutherford Appleton Laboratory. Once built they were integrated with the receiver backends (University of Cantabria, Santander and Barcelona), the feed horns (University of Milan, Italy), the phase switches (Instituto de Astrofisica de Canarias, Tenerife), and waveguides (designed in Italy and built in the USA). The radiometers were assembled in Milan by the company Laben, then delivered to the European Space Agency for installation in the Planck Spacecraft.

Some members of JBCA are involved in the other focal instrument, HFI. First at Cardiff University and now at the University of Manchester, they have played a major role in the design, development and calibration of the Focal Plane Unit, in particular the cold optics, in collaboration with the Institut d'Astrophysique Spatiale - France, Maynooth University - Ireland and JPL/Caltech - USA.

The Science and Technology Facilities Council (STFC) has invested £13M in Herschel and £17.4M in Planck.


For more information please contact

Dr Althea Wilkinson,
The University of Manchester,
+44 (0)161 275 4184.

Julia Short,
BNSC Press Office,
+44 (0)1793 442 012

Jan Tauber, Planck Project Scientist
Research and Scientific Support Department,
Directorate of Science and Robotic Exploration
European Space Agency