[...]... near-circular orbit – these are just two of many of the Solar System s properties that might have been very different had things not gone the way they had Still, the general picture of stars and planets forming from rotating discs seems well established More than any other theory, the nebular hypothesis is the one that fits the data This is the model that I assume in this book Story of the Solar System But this... with time They start off small, grow steadily taller, reach a sort of plateau, grow wrinkled and bent – those that don’t age gracefully! – and then cease to exist It’s the same with the stars There are so many of them, each at different stages in their evolution, that taken together they tell a story – the story of the life of a single, general star, from the cradle to the grave And so it is by theorising,... opposite: The modern theory for the origin of the Solar System is based on models proposed in the eighteenth century by Kant and Laplace Known as the nebular hypothesis, it proposes that the Sun, the planets, the asteroids and the comets all formed at the same time when a cloud of interstellar material collapsed under gravity and flattened out because of rotation The Sun formed at the centre, and the planets... Solar System – so-called exoplanets or extrasolar planets, surrounding other stars – and they are doing so at an alarming rate Already, in just five years, the number of known planetary systems has climbed from zero to dozens The trouble for the nebular model is that, although it accounts for many of the properties of the Solar System, it fails to reproduce the detailed characteristics of many of these... again the rapid rotation Some of the gas dragged out of the Solar Nebula disc would have plummeted towards the star’s surface But not all of it Because the Sun was by now spinning very quickly, some of the gas pulled out of the disc plane was hurled radially outwards, much as water is spun out of the wet clothes in a spin dryer The result was a steady flow of gas away from the star’s surface However the. .. virtue of their stronger gravity, and the original cloud fragmented into hundreds or even thousands of small, dense cores Most of them would later form stars One of them was destined to become the Sun By now, the cloud core from which the Sun would form was perhaps a tenth of a light-year across, more than a hundred times the present size of the Solar System out to Pluto Gradually, this tight clump of. .. connected, vast globs of gas were wrenched out of the surface of the disc and sucked along the field lines, right into the young Sun And where these packets of gas hit, the troubled star responded with the violent flares that are the hallmarks of the T-Tauri phase of star formation Thus the adolescent Sun was very much more violent than the star we know today It looked the part too Its larger, cooler surface... about the Solar System s origins Indeed, this is only part of the story of the Solar System, covered comprehensively in step-by-step fashion in Parts 1 and 2 Part 3 also touches on this issue, but is largely concerned with presenting a detailed inventory and cross-comparison of the Solar System s contents, and an analysis of how they have changed and evolved since birth Lastly, Part 4 looks to the future... the age of our Milky Way galaxy, are very small indeed If correct, the more recent of the two encounter theories would have us believe that our Solar System is a rarity, the happy outcome of a sheer coincidence, and thus one of just a handful in the galaxy of 200 billion stars to which our Sun belongs But as we shall see below, planetary systems are the norm, not the exception Again, this theory does... kilometres The disc would have contained about 1–10 per cent of the current mass of the Sun – most of it in the form of gas, with about 0.1 per cent of a solar mass locked up inside particles of dust Near the centre of the disc, close to the seething protosun, the temperature may have exceeded 2000 Celsius Here, where things were hot and important, the disc may have been hot enough to emit its own visible . age, and beyond. These and other issues are all part of a great story – the story of the Solar System. Overview of the Solar System What is the shape of the Solar System? Where are the various objects within. intro- duction to theories of the formation and structure of the Solar System, the book illustrates the birth of the Sun, and then explains the steps that built up the bodies of the Solar System. With the. that the centre of our planetary system is solar territory. It is the residence of the yellow star that we call the Sun – not the Earth or any of the other major bodies that comprise the Solar System.