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Headlines Published on 31 December 2007

TitleMapping the Milky Way

Spectacular images of our own galaxy, the Milky Way, have been released by the UK-led INT/WFC Photometric Hα (Hydrogen-alpha) Survey of the Northern Galactic Plane (IPHAS) consortium. This collaboration of over 50 astronomers, which includes partners from Europe, the USA and Australia, has compiled the first comprehensive optical digital survey of the Milky Way. This was accomplished by studying light emitted by hydrogen ions, using the Isaac Newton Telescope on La Palma, in the Canary Islands. The observations will be used to construct a three-dimensional map of our home galaxy.

This is an image of the centre of the Rosette Nebula, as imaged in Hydrogen-alpha emission in the IPHAS survey.
© Nick Wright, University College London
This is an image of the centre of the Rosette Nebula, as imaged in Hydrogen alpha emission in the IPHAS survey.
© Nick Wright, University College London
The IPHAS survey is described in a paper submitted to the Monthly Notices of the Royal Astronomical Society and includes some 200 million unique stars, revealing how the more unusual varieties are born, evolve and die. This enormous resource will facilitate studies of the stellar demographics of the Milky Way and its three-dimensional structure. Prof. Janet Drew of the University of Hertfordshire said, 'Using the distinctive Hydrogen marker, we are able to look at some of the least understood stars in the Galaxy — those at the early and very late stages of their life cycles. These represent less than one in a thousand stars, so the IPHAS data will greatly improve our picture of stellar evolution.'

Recent changes have been made in the way that astronomers share data. As well as being available with the commonly used Web access, it is also being published through a Virtual Observatory interface. The data can now be automatically cross-referenced with other relevant data catalogues. Dr Nic Walton of the University of Cambridge said: 'Using the standard Virtual Observatory interface is a very effective way of exploiting the IPHAS survey data. This is a substantial and significant survey, which aims to eventually contain 700 million to 800 million objects. Access through the AstroGrid Virtual Observatory opens up a full range of analysis options and should allow astronomers to make greater use of the information. IPHAS is the largest dataset published primarily through Virtual Observatory interfaces to date, and as such heralds the future of survey data mining.'

The observations show the distribution of glowing hydrogen, the most common element in the universe, in the star-filled section of the Northern Plane of the Milky Way. This is achieved using a filter sensitive to the emission of hydrogen in the red part of the spectrum, known as H-alpha (Hydrogen-alpha) emissions. This will enable — for the first time — the detailed study of large numbers of dying stars such as white dwarfs, planetary nebulae and supernovae remnants. The IPHAS dataset is proving to be a treasure trove for scientists. Astronomers from the University of Southampton are leading an effort to catalogue the brighter H-alpha emission line stars revealed so far by the survey. The distribution of these special objects across the northern sky traces "hot spots" of recently formed stars in our Galaxy much more effectively than was previously possible.

More information:

  • The IPHAS consortium
  • 'Telescope station takes up work'

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