NARVAL@TBL: the first observatory dedicated to stellar magnetism

NARVAL has just been installed on Télescope Bernard Lyot[1] atop Pic du Midi. Like ESPaDOnS, its twin brother mounted on Canada-France-Hawaii Telescope[2], it is a stellar spectropolarimeter, ie an astronomical facility constructed and optimised for studies of stellar magnetic fields and their effects on the life of stars and their surrounding planets. Thanks to NARVAL, the Télescope Bernard Lyot becomes the first observatory worldwide dedicated to these studies. And since the Sun sets in Hawaii when it rises on the Pyrenees, NARVAL and ESPaDOnS, when working together, can continuously stare at magnetic stars to discover the secrets of their lives!
A new observing night starts at Télescope Bernard Lyot atop Pic du Midi, on which NARVAL, the ESPaDOnS twin spectropolarimeter, was just installed.
A complex network of magnetic field lines is emerging from the surface of the baby star SU Aurigae. This image was obtained thanks to the combined effort of NARVAL and ESPaDOnS. Click on the image to animate the star. (© JF Donati, MM Jardine).

"Magnetic fields are essential ingredients in the life of stars. They are both tracers of their history, and actors of their evolution" explains Pascal Petit, young astronomer at the Laboratoire d'Astrophysique de Toulouse-Tarbes (CNRS, Université Paul Sabatier, Observatoire Midi-Pyrénées) and NARVAL project scientist. "For instance, we think that the magnetic field of the Sun could be the cause of the Little Ice Age, a period of several decades in the mid 17th century during which winters were unusually cold over Europe. Even more spectacular is the way magnetic fields manage to influence how stars are born, by modifying the amount of material from which they form. However, we still know very little about these stellar magnetic fields - even the field of the Sun is still a mistery to us!" says Pascal Petit.

"Thanks to NARVAL, we now have an instrument and a telescope dedicated to the study of stellar magnetic fields" says Michel Aurière, astronomer at the Laboratoire d'Astrophysique de Toulouse-Tarbes and NARVAL project manager. "ESPaDOnS is only available a small fraction of the time, sharing nights at Canada-France-Hawaii Telescope with other highly popular instruments. The advent of NARVAL, the ESPaDOnS twin, allows to overcome this limitation and gives astronomers the possibility of carrying out much more ambitious projets than before." "Scientists from many different countries had perfectly understood this issue, and massively joined from the very moment NARVAL was opened to the community", tells David Mouillet, former director of TBL.

To demonstrate the power and complementarity of NARVAL, SU Aurigae, a baby star located at about 450 light-years from the Sun, was looked at continuously with both NARVAL and ESPaDOnS[3]. "With an age of only a few million years, SU Aurigae is about 1000 times younger than the Sun" explains Jean-François Donati, directeur de recherche at CNRS and inventor of ESPaDOnS and NARVAL. "At this age, a star is not yet completely formed and continues to attract surrounding material. Once captive in the magnetic web of the star, the material is redirected towards the surface of the star along magnetic field lines like beads on a wire. These observations tell us that the magnetic web of SU Aurigae is much more complex that previously guessed through theoretical models of stellar formation, says Jean-François Donati.

The NARVAL[4] project was carried out by the technical teams of the Télescope Bernard Lyot and the Laboratoire d'Astrophysique de Toulouse-Tarbes; it benefitted from the unique worldwide scientific and technical expertise that the Toulouse team accumulated in this field of research during the last decade. Integrated in Tarbes, NARVAL was then installed and successfully tested at Pic du Midi in fall 2006, then offered to the international scientific community in 2006 December. The cost of NARVAL, about 1 M€, was funded by the Région Midi-Pyrénées and the Ministère de la Recherche (in the framework of a Contrat de Plan Etat-Région), the conseil Général des Hautes Pyrénées, the European Union (FEDER funds) and the CNRS Institut National des Sciences de l'Univers (INSU).

Jean-François Donati, inventor of NARVAL/ESPaDOnS, tel: (33) 561332917
Michel Aurière, NARVAL project manager, tel: (33) 562566019
Pascal Petit, NARVAL project scientist, tel: (33) 561332828
Rémi Cabanac, TBL director, tel: (33) 562566038

CNRS/INSU press release (in french)
NARVAL webpage
ESPaDOnS webpage
TBL wepage (in french)
Pic du Midi webpage (in french)
[1] The 2m Télescope Bernard Lyot (TBL) is funded by the CNRS Institut National des Sciences de l'Univers (INSU)
[2] The Canada-France-Hawaii Telescope (CFHT) is financé by INSU/CNRS, the National Research Council of Canada and the University of Hawaii.
[3] This result was obtained in the framework of a international research project led by Jean-François Donati (LATT, Observatoire Midi-Pyrénées, CNRS/Université Paul Sabatier) and involving Pascal Petit and Frédéric Paletou (LATT), Jérome Bouvier, Jonathan Ferreira, Catherine Dougados and François Ménard (LAOG, Observatoire de Grenoble, CNRS/Université Joseph Fourier) UK astronomers Moira Jardine, Andrew Cameron, Tim Harries, Gaitee Hussain and Yvonne Unruh.
[4] NARVAL was constructed by the technical teams of the Télescope Bernard Lyot - namely Christophe Montheil (optomechanics), Laurent Guesdon (electronics), Philippe Ambert and Thierry Louge (instrument control) - the LATT - namely Laurent Parès (optics), Gérard Gallou (mechanics), Patrick Couderc and Francis Beigbeder (detector) - and the OMP - namely René Dorignac (mechanics). The NARVAL project was supervised by Michel Aurière (project manager), Pascal Petit (project scientist), David Mouillet (former TBL director), Francis Lacassagne (logistics), Jean-Pierre Dupin (scheduling) and Jean-François Donati (technical and scientific expertise).
© Jean-François Donati, last update Feb 01 2007