A Set 10 Model
Planetarium is a specific name for an orrery which contains the Sun and all known planets. Orreries were first built in the early eighteenth century; of necessity they did not include Neptune (discovered 1846) and Pluto (discovered 1930). Latterly of course many other bodies have been discovered in our Solar System. It is thus quite possible to be a pioneer in the field of orreries by constructing a 'first* - the subject of this Modelplan which includes Quaoar, discovered in 2002. Quaoar (pronounced kwa-whar) orbits the Sun in a near perfect circle with a period of 288 years. It has a diameter of about 1300 km - more than half the diameter of Pluto. Quaoar dwells in the Kuiper Belt, an icy debris field of comet-like bodies extending 5 billion km beyond Neptune's orbit. A further large body -Sedna - was discovered in the Kuiper Belt in November 2003, but this is not very interesting for the Meccano modeller as its period is about 10,500 years and its progress would be very slow in any Meccano model. It was noted in MP156 that the Saturnilabe was an attempt to show that quite a complex orrery could be achieved with the relatively modest collection of gears in Set 10; this present Planetarium must be close to the ultimate in this regard as almost all of the gears and sprockets in Set 10 are used and still the desirable aim of accuracy to 1 has been achieved.