Astronomers have discovered vast comet belts surrounding two nearby planetary systems – GJ 581 and 61 Vir – known to host only Earth-to-Neptune-mass worlds.   Previously, scientists found that the dusty belt surrounding nearby star Fomalhaut must be maintained by collisions between comets. 


Two planets are confirmed around G-type star 61 Vir, which is just a little less massive than our Sun. The planets in both systems are known as 'super-Earths', covering a range of masses between 2 and 18 times that of Earth.

 Artist's impression of the debris disc and planets around the star known as Gliese 581, superimposed on Herschel PACS images at 70, 100 and 160 micrometer wavelengths. The line drawing superimposed on the Herschel image gives a schematic representation of the location and orientation of the star, planets and disc, albeit not to scale. The black oval outline sketched onto the Herschel data represents the innermost boundary of the debris disc; the approximate location of the outermost boundary is represented by the outer set of dashed lines. It is not possible to identify the central star due to smearing of the Herschel data. GJ 581's planets have masses between 2 and 15 Earth masses and are all located within 0.22 Astronomical Units (AU, where 1 AU is the distance between Earth and our Sun) of the central star. A vast debris disc extends from approximately 25 AU to 60 AU. Background galaxies are also visible in the Herschel field-of-view. Credit: ESA/AOES







