first scientific result

Magnetic field of the baby star SU Aur, as derived from coordinated NARVAL/ESPaDOnS osbervations. Click on image to animate star. (© JF Donati, MM Jardine).

The magnetic field of a baby star

Although just offerered to the astronomical community (in Dec 2006, on a 'shared-risk' policy), NARVAL has already contributed to obtain a significant scientific result. On late November and early December 2006, NARVAL and ESPaDOnS simultaneously observed SU Auriga, a newly-born star weighting about twice as much as the Sun and located at a distance of about 450 light years from us. With an age of only a few million years (as opposed to 5 billion years for the Sun), SU Aur is still in its extreme infancy.

Baby stars like SU Aur are not yet completely formed and still accrete mass from the protostellar disc that surrounds them. Magnetic field is what connects the star to its surrounding disc, with material flowing from the inner disc rim to the stellar surface along field lines as beads along wires. Magnetic fields thus impact the way stars are formed.

Existing models of stellar formation assume that the magnetic field of baby stars is fairly simple, resembling that of a simple magnet bar or that of the Earth. The new observations of SU Aur collected with NARVAL and ESPaDOnS suggest that accretion processes in protostars are significantly more complex than previously thought.

These data were collected in the framework of a French/UK project aimed at studying magnetic fields of baby stars. This project is led by JF Donati (Observatoire Midi-Pyrenees) and involves astrophysicists from UK (M Jardine, A Cameron, T Harries, G Hussain and Y Unruh), from Grenoble (J Bouvier, J Ferreira, C Dougados, F Ménard) and from Toulouse (P Petit, S Jeffers, F Paletou).

© Jean-François Donati, last update Jan 20 2007.