Complex magnetic footprints on an infant star

Scottish and French astronomers have found a star with a fossilised magnetic field, left over from the time when the star formed.

Our own Sun regenerates its magnetic field every 11 years, so little trace remains of its beginnings. The massive star, studied by the University of St Andrews, formed only 1 million years ago and is so young that the fossil remnant has not yet been erased. The discovery may shed some light on the way in which the Sun generates its magnetic field and on the conditions that prevailed at the birth of our own solar system.

The study – led by the Observatoire Midi-Pyrenees in Toulouse – is reported in the current edition of ‘Monthly Notices of the Royal Astronomical Society’.

University of St Andrews astronomer Dr Moira Jardine said, “The record of the changes in the Earth’s magnetic field is frozen into the rocks of the ocean floor but, for stars, this fossil record doesn’t exist. We have to try to piece together the history of the Sun’s magnetic activity by looking at other, younger stars. This one star in particular is a good example as, like all very massive stars, it doesn’t have the internal turbulent motions that might smear out the record of its earliest field. What has been found is a complete surprise – we had expected to find a simple field (rather like the Earth’s), but instead we found a complex magnetic field that is much closer to the one our present-day Sun produces. This surprising discovery may help us to understand the different ways that young stars can produce their magnetic fields”.

The star (Tau Scorpii) is so bright and so close (at a distance of only 400 light years) that it can be seen with the naked eye. It is about five to six times bigger (and hotter) than our own Sun, and weighs as much as 15 Suns put together.

ENDS

NOTE TO EDITORS

Image of Tau Scorpii available from Claire Grainger, contact details below.

For more information, please contact Moira Jardine, School of Physics and Astronomy – telephone 01334 463146

Or

Jean-Francois Donati Laboratoire d’Astrophysique, Observatoire Midi-Pyrenees 14 avenue Edouard Belin, F-31400 Toulouse, France Tel: (33) 561332917 Fax: (33) 561332840 e-mail: jean- [email protected]

Further information available at:

http://www.ras.org.uk http://www.ast.obs- mip.fr/users/donati//press/tausco_e ng.html http://www.ast.obs- mip.fr/projets/espadons/espadons.ht ml

Issued by Beattie Media – www.beattiegroup.com On behalf of the University of St Andrews For more information, please contact Claire Grainger, Press Officer – 01334 462530, 07730 415 015 or [email protected]; Ref: press releases/moirajardine View the latest University news at http://www.st-andrews.ac.uk