Département des accélérateurs, de cryogénie et de magnétisme

Sirius, the brightest star of the sky is a puzzling star.  A possible colour change is reported for the star in historical times which cannot be explained by normal stellar evolution. This has led to the hypothesis of a possible  and yet undetected small companion.
Using the modern technique of adaptative optics which allow to suppress most of the blurring of the atmosphere, J.M. Bonnet-Bidaud and E. Pantin of the Astrophysical Department of CEA-Irfu have now obtained the first and most sensitive image in the infrared domain where the smallest stars are most easily detected.
The resulting high contrast image obtained at high spatial resolution (0,2 arcsecond) has not revealed any small object at a distance from Sirius ranging from 6 to 33 U.A (1 U.A is the Earth-Sun distance). The image is deep enough to exclude objects of planet sizes so that at least no big planets orbit Sirius in outer part of the image. However, a small infrared excess is measured around the white dwarf Sirius-B, the already known companion of Sirius which may indicate circumstellar material. If planets exist around Sirius, it may well be only planetary debris around this small companion. The results are published in the Astronomy and Astrophysics Journal.