Powerhouse of the Solar System
The Sun is our local star - a nuclear reactor at the hub of the Solar System. Each second, the Sun loses four million tonnes of mass – energy that will keep the Sun blazing for another five billion years. Yet the Sun, overall, is no denser than yoghurt, a cauldron of incandescent gas spewing flares and prominences. Electrically charged particles stream from the Sun – the solar wind. Twists in the magnetic field trigger gigantic ejections that turn the wind into a storm.
2. Inside Track
Mercury, closest planet to the Sun
Of the nine planets, Mercury orbits on the inside track – the closest planet to the Sun. Baked and irradiated, Mercury is a cratered little world – a pristine record of the impactors that rained from space during the early Solar System. Mercury is weird. It has double sunrises and a day twice as long as its year. Even stranger, there may be ice in deep craters at the poles – deposited by comets and perpetually shadowed from the scorch of the Sun.
Planet from Hell
Venus is Earth gone wrong - a lifeless planet with a dense and choking atmosphere and temperatures to melt lead. Constantly shrouded in cloud, Venus could once have been Earth’s twin with oceans and continents, even simple life. But there is a theory that as the Sun matured and its luminosity increased, Venus became hell. Today it is a brutal landscape entirely resurfaced by molten lava oozing from thousands of volcanoes. Venus is the hottest planet.
We live on the largest inner planet, third from the Sun and the first with a moon. Earth is lucky – at just the right distance from the Sun for life to evolve in the oceans, for green plants to produce breathable air and for humankind to develop agriculture and civilization. But from space there is no sign of the six billion people on Earth. All that is seen are vast oceans, weather systems, daily and seasonal changes and beautiful continents drifting imperceptibly.
Our Partner in Space
The Moon was probably formed when a body the size of Mars twice hit early Earth. The first collision was a glancing blow. The second, two days later, was a major impact that threw enough material into orbit to form the Moon. Since then, the Moon has been steadily receding. Eventually it will be so distant that Earth will start to wobble and our climate, deprived of its lunar regulator, will become chaotic. The Moon – cratered, airless and inert - is nevertheless our vital partner in space.
Eclipses and Aurorae
A total eclipse of the Sun is the greatest spectacular in the Solar System. It happens when the Moon, which is 400 times smaller than the Sun, completely obscures the Sun, which is 400 times farther from us than the Moon – an astonishing celestial coincidence. Nature has another light show – the aurora. A swirling kaleidoscope of colour, it is seen at night around the polar regions when electrified particles from the solar wind interact with Earth’s upper atmosphere.
7. Red Planet
Mars, the red planet, is the world on which next we will walk. The Martian day is a comfortable 24-and-a-half hours. But the rest is strange – planet-wide duststorms, temperatures overnight of minus 100 degrees and a daytime high just above freezing. Mars has the biggest volcano in the Solar System, Olympus Mons, and the largest geological fault, Mariner Valley. Water once flowed on this arid planet. Possibly, there was life. So what happened?