But the interesting thing about Gliese 581 and 61 Virginis is that neither appear to contain large gas giant worlds - the largest is a Neptune-class world. This means that the Kuiper Belt-like features surrounding both stars are heavily populated with cometary embryos that never left home.
After careful analysis, the space telescope deduced that the cometary belts are ten-times more populated than our Kuiper Belt. It did this by observing the faint infrared glow of dust contained inside the star systems' belts.
"The new observations are giving us a clue: they're saying that in the solar system we have giant planets and a relatively sparse Kuiper Belt, but systems with only low-mass planets often have much denser Kuiper belts," says Mark Wyatt from the University of Cambridge, UK, lead author of the 61 Virginis paper.
Herschel is no stranger to detecting evidence of comets in other star systems. Earlier this year the telescope trained its eye on the famous star Fomalhaut.
By looking at the infrared radiation from its vast dusty disk, astronomers were able to estimate how many comets must be continually destroyed (through comet-comet collisions and strikes with hypothetical planetary bodies) to supply the dust surrounding the star. 260 billion to 83 trillion comets are thought to be bumping around in Fomalhaut's belt, a similar number of comets that are thought to be contained in the solar system's Oort Cloud.