The Oort cloud /ˈɔərt/, or the Öpik–Oort cloud (Finnish: [ˈøpik.ˈoːrt]), is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun. The Kuiper belt and the scattered disc, the other two reservoirs of trans-Neptunian objects, are less than one thousandth of the Oort cloud's distance. The outer limit of the Oort cloud defines the cosmographical boundary of the Solar System and the region of the Sun's gravitational dominance.
The Oort cloud is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane. Astronomers believe that the matter composing the Oort cloud formed closer to the Sun and was scattered far out into space by the gravitational effects of the giant planets early in the Solar System's evolution.
Philip Stott is a professor emeritus of biogeography at the School of Oriental and African Studies, University of London, and a former editor (1987–2004) of the Journal of Biogeography.
In the early 1970s, Stott and his wife, a historian and biographer, lived in Thailand and he was carrying out field research at Kalasin. He has two daughters.
He has written academic papers and books on chalk grassland, on the vegetation and archaeology of Thailand (and on the rest of southeast Asia), on ecology and biogeography (e.g. his textbook 'Historical Plant Geography'), on fire ecology e.g. on lichens and mosses, on tropical rain forest e.g. and and on the construction of environmental knowledge.
He is currently Chair of The Anglo-Thai Society, UK. He is no longer a member of the Scientific Alliance because he deems it important to be academically independent of all organisations, industry, and green groups.
In the UK, he is a life-long Labour supporter and he is mildly left wing politically. He is fiercely anti-tobacco.[citation needed]