Imperial College London - New star survey sheds light on the evolution of galaxies

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The first survey of the entire northern Milky Way for forty years is shedding fresh light on the life-cycle of stars in our astronomical backyard.

The survey, which publishes its initial findings today in the Monthly Notices of the Royal Astronomical Society, uses the latest high resolution instruments to seek out stars and nebulae in the early and late phases of their evolution, stages that are rarely observed because they are so short-lived. Lead researcher Professor Janet Drew, of the Department of Physics at Imperial College London, says:

"These are crucial evolutionary stages in the growth and death of planetary systems, and many of the major unsolved problems in stellar evolution are to do with the fact that we have had relatively few examples to work with.

"The last time the northern Milky Way was searched in a concerted way was the 1960s, using much smaller telescopes and now obsolete detection methods. This new survey has the potential to greatly expand our understanding of how our own Solar System came to be and what it will become."

The UK, Dutch and Spanish team is using the 2.5 metre Isaac Newton Telescope (INT) to detect stars and bodies of gas that emit strongly at the wavelength of red light called H alpha. H alpha is emitted by excited atoms of hydrogen, allowing scientists to pick out both young, potential planet-building systems and old objects that will soon become compact white dwarfs or supernova explosions.

These are particularly important in understanding the evolution of galaxies, since youthful stars help to shape the growth of planetary systems while those in old age recycle energy and chemically enriched matter back into the galactic environment as they collapse.

The new survey reaches beyond the sun's orbit around the centre of the Milky Way to a radius of 30 kiloparsecs (kpc) around 90,000 light years. Currently almost nothing is known about the star populations beyond a distance of about 15 kpc. Professor Drew adds:

"At the moment, very little is known about the far reaches of the Milky Way's disc there's still uncertainty in its spiral arm structure, and we don't really know where the stars run out. Recent technical developments, which have boosted both the efficiency of large-scale astronomical surveys and their quality in a major way, mean we now have the opportunity to survey the galaxy we live in at hugely improved sensitivity."

The INT Photometric H Alpha Survey of the Northern Galactic Plane (IPHAS), Monthly Notices of the Royal Astronomical Society, Volume 362, Issue 3, pp 753-776.

Janet E Drew1, R Greimel2, M J Irwin3, A Aungwerojwit4, M J Barlow5, R L M Corradi2, J J Drake6, B T Gansicke4, P Groot7, A Hales5, E C Hopewell1, J Irwin3, C Knigge8, P Leisy9, 2, D J Lennon2, A Mampaso9, M R W Masheder10, M Matsuura11, L Morales-Rueda7, R A H Morris10, Q A Parker12,13, S Phillips10, P Rodriguez-Gil4,9, G Roelofs7, I Skillen2, J L Sokoloski6, D Steehgs6, Y C Unruh1, K Viironen9, J S Vink1, N A Walton3, A Witham8, N Wright5, A A Zijlstra11 and A Zurita14

1 Imperial College London
2 Isaac Newton Group of Telescopes
3 Cambridge University
4 University of Warwick
5 University College London
6 Harvard Smithsonian Center for Astrophysics
7 Radboud Universiteit Nijmegen
8 University of Southampton
9 Instituto de Astrofisica de Canarias
10 Bristol University
11 University of Manchester
12 Macquarie University
13 Anglo-Australian Observatory
14 La Universidad de Granada

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