The outer Oort cloud may have trillions of objects larger than ,[REF] and billions with absolute magnitudes[REF] brighter than 11 (corresponding to approximately diameter), with neighboring objects tens of millions of kilometres apart [REF].
If analyses of comets are representative of the whole, the vast majority of Oort-cloud objects consist of ices such as water, methane, ethane, carbon monoxide and hydrogen cyanide [REF].