2017 Olivier Chesneau Prize Awarded to Rachael Roettenbacher

3 May 2017

The 2017 Olivier Chesneau Prize has been awarded to Rachael Roettenbacher, for her doctoral thesis entitled “Shifting the Starspot Paradigm through Imaging Magnetic Structures and Evolution”. She is currently a postdoctoral researcher at Stockholm University, having obtained her PhD at the University of Michigan (Ann Arbor, USA) in 2016.

Established by ESO and the Observatoire de la Côte d’Azur (OCA), the Olivier Chesneau Prize commemorates the astronomer Olivier Chesneau [1] and is awarded for the best PhD thesis in High Angular Resolution Astronomy. Rachael Roettenbacher is the second recipient of the prize, after Julien Milli in 2015.

Rachael impressed the board with her study of the magnetically active star, Zeta Andromedae. The star is located about 190 light-years from Earth and has a radius approximately 15 times larger than the Sun’s. Making use of the power of interferometry, combining six different telescopes to produce images of extraordinarily high resolution, Rachael studied starspots on Zeta Andromedae. By taking measurements throughout the 18-day rotation period of the star, she was able to make a time-lapse of the starspots, creating what Rachael describes as the “highest quality images of a star we have other than the Sun”.

Her work shows that these cooler, darker areas on the star’s surface are not limited to the bands just above and below the equator, as they are on the Sun. Instead, Rachael found a vast network of spots, demonstrating the global effects that strong magnetism has on the surface of these stars. Starspots form when strong magnetic fields block the flow of energy coming from the stellar core and this new result indicates that astronomers need to be careful when estimating the temperatures of magnetically active stars. Her work was published in Nature, in May 2016.

The award will be presented at a ceremony in July.


[1] Olivier Chesneau (1972–2014) was a talented scientist who was animated and passionate about his subject. He led pioneering work using visible and infrared long-baseline interferometry to study disc formation around many astrophysical objects, including evolved massive stars, planetary nebulae and novae. His foremost results include the study of the environments close to Eta Carinae and other massive stars, the first direct detection of discs in planetary nebulae, finding evidence of dust bipolar ejections by novae shortly after eruption, and the discovery of the largest yellow hypergiant star in the Milky Way. His findings were often widely publicised through press releases from ESO and CNRS-INSU. The 2012 Michelson Prize of the International Astronomical Union and of Mount Wilson Institute was awarded to Olivier Chesneau for major contributions in stellar astrophysics made with long-baseline interferometry.



Philippe Stee
Director, Lagrange Laboratory
Observatoire de la Côte d'Azur, Nice, France
Tel.: +33 4 92 00 31 17

Marc Fulconis
OCA, Public Information Officer
Observatoire de la Côte d'Azur, Nice, France
Tel.: +33 4 92 00 19 70

Antoine Mérand
VLTI Programme Scientist
ESO, Garching, Germany
Tel: +49 89 3200 6630

Peter Grimley
ESO Assistant Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6383

About the Announcement



Rachael Roettenbacher, winner of the 2017 Olivier Chesneau Prize
Rachael Roettenbacher, winner of the 2017 Olivier Chesneau Prize
Map of the star zeta Andromedae
Map of the star zeta Andromedae