Free Astronomy Magazine September-October 2014

EXOPLANETS trographs in the world, the ESO’s HARPS and the Keck Observatory’s HIRES. Unlike what was done in previous works, Robert- son and colleagues focused their attention on the magnetic surface activity of the star, to assess whether and to what extent the presence of active regions could have “con- taminated” the star’s radial velocity mea- surements by mimicking the presence of planets. This is a key point that needs to be further examined in order to better under- stand the topic being discussed. In the vast majority of cases, the certainty of the existence of a planet it is had at the A bove, a syn- thetic repre- sentation of the electromagnetic spectrum with a magnification of the visible region, showing in the red band the po- sition of the H α line utilized by Paul Robertson’s team to prove that GJ 581 has only 3 planets. The diagram on the right shows instead the ef- fects of the radial velocity variation, with the light’s wavelength short- ening (blue) and lengthening (red) depending on the direction in which the planet pulls the star. [ESO]