Formation and evolution of the Solar System energy from the fusion of hydrogen into helium in their cores. The Sun remains a main-sequence star today. The various planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is accretion, in which the planets began as dust grains in orbit around the central protostar. Through direct contact, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies (planetesimals) of ~10 kilometres (km) in size. These gradually increased
Wonders of the Solar System on the matter that composite the rings - a phenomenon called orbital resonance. The third episode looks at the atmosphere of the planets and moons of the Solar System, with Earth, Mars, and Venus being the main focus. The episode starts with Cox travelling to South Africa and taking a journey in an English Electric Lightning up to an altitude of 18 kilometres where the "thinness and fragility" of the atmosphere could be observed in the middle of the day. This is then contrasted with the planet-wide consequences of Mercury's depleted, and Venus' broiling greenhouse atmospheres. Later, the dunal morphology