First Spectroscopic Detection of Surface Structures on a Normal A-Type Star - The Case of Vega

International audienceFor the first time the existence of spots on the surface of the intermediate mass star Vega has been shown. This unexpected result sets new important constraints on the stellar evolution of intermediate mass stars and in particular on the magnetic field generation mechanisms. Vega (α Lyrae) is an intermediate mass star (spectral class A0) in rapid rotation (Prot = 0.68 d). Since more than 150 years it is a stability reference for photometry. Despite the fact that very small sporadic light variations had been announced in the past, no periodicity had been detected in its light curve. In 2009 a very faint magnetic field has been detected on Vega (Lignières et al., 2009, A&A, 500L, 41) and subsequently also on other stars of the same spectral class (A). While the solar magnetic field is generated by a dynamo mechanism in its convective envelope, the origin of magnetic field in stars exempt of convective envelopes, such as Vega, remains mysterious. One of the characteristics of the solar dynamo is its temporal variability revealed by the appearance or disappearance of solar spots. Are there similar structures on the surface of Vega? 2015 A&A, 577, 64. & Nature Research Highlight