There are still quite a lot of unsolved mysteries in our neighbourhood, the Solar System. Astronomers knowvery little, for instance, about the so-called 'transneptunian objects': a ring of asteroid-type bodies located beyond planet Neptune. Dutch astronomer Gerald Kuiper predicted the existence of this 'belt' fifty years ago - it is therefore named the 'Kuiper belt'-, but the first detection of one of its constituent bodies only happened in 1992. Further surveys have provided an estimate of how many objects are actually there: possibly 10.000 bodies with a diameter larger than 300 kilometres, and maybe three million larger than 30 kilometres in diameter. Only 300 of them have been observed so far. The list of pending questions about them is very long: what's their precise origin and composition? Which of the comets that periodically visit the Earth are 'Kuiper objects'? ESA's next infrared space telescope, the Herschel Space Observatory - formerly called 'FIRST' - will help to provide the answers, astronomers gathered in Toledo (Spain) said yesterday.