the Milky Way
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.
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
stages of their life cycles. These represent less than one in a
thousand stars, so the IPHAS data will greatly improve our picture of
|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
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
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.
station takes up work'