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Scientists show how bright galaxies stick together

A false-colour Herschel image of the Lockman hole. Almost every point of light is an entire galaxy, containing billions of stars

University of Sussex physicists and partners have today revealed the latest findings from the Herschel space observatory.

For more than a decade, astronomers have puzzled over strangely bright galaxies in the distant Universe. These 'luminous infrared galaxies' appear to be creating stars at such phenomenal rates that they defy conventional theories of galaxy formation.

Now the European Space Agency's Herschel infrared space observatory, with its ability for very sensitive mapping over wide areas, has seen thousands of these galaxies and pinpointed their locations, showing for the first time that they are packing themselves closely together, forming large clusters of galaxies by the force of their mutual gravity.

Thousands of galaxies crowd into the Herschel image (above) of the distant Universe. Each dot is an entire galaxy containing billions of stars.

The mottled effect in the image gives away this clustering. All the indications are that these galaxies are busy crashing into one another, and forming large quantities of stars as a result of these violent encounters.

This image is part of the Herschel Multi-tiered Extragalactic Survey (HerMES) Key Project, which studies the evolution of galaxies in the distant, ancient Universe. The project uses the SPIRE (Spectral and Photometric Imaging REceiver) instrument on Herschel and has been surveying large areas of the sky, currently totalling 15 square degrees, or around 60 times the apparent size of the Full Moon.

Professor Seb Oliver, of the University of Sussex, a co-leader on HerMES, presented the result s at the Herschel First Results Symposium in the Netherlands.  He says: "This result is fantastic. It is just the kind of thing that we were hoping for from Herschel and was only possible because we can see so many thousands of galaxies. It will certainly give the theoreticians something to chew over."

This particular image was taken in a region of space called the Lockman hole, which allows a clear line of sight out into the distant Universe. This 'hole' is located in the familiar northern constellation of Ursa Major, The Great Bear.

The galaxies seen in this image are all in the distant Universe and appear as they did 10-12 billion years ago. They are colour-coded in blue, green, and red to represent the three wavebands used for Herschel's observation.

Those appearing in white have equal intensity in all three bands and are the ones forming the most stars. The galaxies shown in red are likely to be the most distant, appearing as they did around 12 billion years ago.

Team member Dr Lingyu Wang, of the University of Sussex says: "With Herschel, we are able to pierce through huge amounts of dust and study the impact of the environment right from the birth of these massive galaxies, which are forming stars at colossal rates."

HerMES will continue to collect more images, over larger areas of the sky, to build up a more complete picture of how galaxies have evolved and interacted over the past 12 billion years.

Notes for Editors

For more information, please visit: (HerMES project website at the University of Sussex) (UK Herschel website)

For images: (Online Showcase of Herschel Image)

For information about Physics and Astronomy at the University of Sussex:

For interviews contact the University of Sussex Press office: Tel: 01273 678 888 or email


Last updated: Wednesday, 26 May 2010