Picture captures a billion stars

(By Jonathan Amos Science correspondent, BBC News, Manchester)

Scientists have produced a colossal picture of our Milky Way Galaxy, to reveal the detail of a billion stars. It is built from thousands of individual images taken by two UK-developed telescopes operating in Hawaii and in Chile. Earth sits just in the galactic plane (picture 2)which looks like a very dense but very long strip of stars arcing across the sky.

These are the big objects like clusters, and nebulae - the gas clouds where stars are forming.

"There are about one billion stars in there - this is more than has been in any other image produced before," said Dr Nick Cross from the University of Edinburgh. Dr Cross has presented the new work to the UK National Astronomy Meeting (NAM) in Manchester.

Archived data from the project, known as the Vista Data Flow System, will be examined by astronomers to make new discoveries about the local cosmos. The image concentrates on the dense plane of the galaxy, which is shown as a very long, very thin strip. That makes it virtually impossible to be shown in a clear way on a page. Although

Dr Cross and colleagues have produced an online interactive tool that helps the user to zoom into particular areas. Even then, these smaller fragments of sky will contain thousands of stars.

The project has been 10 years in the making. It combines data from the UKIDSS/GPS (U nited K ingdom I nfra-Red D eep S ky S urvey + Global Positioning System) sky survey made by the UK Infrared Telescope in Hawaii with the VVV (V ista V ariables in the V ia Lactea=Milky Way,Spanish) (VISTA - V isible and I nfrared S urvey T elescope for A stronomy) survey data acquired by the Vista telescope in Chile.

These astronomical facilities view the sky at infrared wavelengths, enabling them to see past of the dust in the Milky Way that will ordinarily obscure observations made at optical, or visible, wavelengths.

UKIRT (United Kingdom Infra-Red Telescope) is responsible for the right end of the image; Vista - Visible and Infrared Survey Telescope for Astronomy - is a reflecting telescope with a 4.1 metre mirror, located at the Paranal Observatory in Chile. It is operated by the European Southern Observatory and saw first light in December 2009) produced the left, including the more extensive block of coverage which traces the centre of the galaxy and its surrounding bulge of stars. (Black squares in the image are data gaps that are in the process of being filled).

Researchers at the universities of Edinburgh and Cambridge processed and archived all the data that explain the big picture, and have made it available to astronomers around the world for future study. Zooming into particular regions opens the detail of thousands of stars.

"There are many uses for this picture," said Dr Cross. "It will help us really understand the true nature of our galaxy, to see where everything is. Here you can look at things on the large scale, to understand how they are related to each other; to look at things that might be across multiple images in a catalogue. These are the big objects like clusters, and nebulae - the gas clouds where stars are forming."

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