Solar System

The solar system is the gravitationally bound system of the Sun and the objects that orbit it either directly or indirectly. For most part of the history, humanity did not recognise or understand the concept of the solar system. Most people up to the easy 1500s believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although the greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nucolaus Copernicus was the first to develop a mathematically predictive heliocentric system.

Later in 17th Century, Galileo discovered that the Sun was marked with sunspots, and that Jupiter had four satellites in orbit around it. Christiaan Huygens follows on from Galileo’s discoveries by discovering Saturn’s moon Titan and the shape of the rings of Saturn. Edmond Halley realised in 1705 that repeated sightings go a comet were recording the same object, returning regularly once every 75-76 years. This was the first evidence that anything other than the planets orbited the Sun. Around the time, the term Solar System first appeared in English. In 1838 Friedrich Bessel successfully measured a stellar parallax, an apparent shift in the position of a star created by Earth’s motion around the Sun, providing the first direct, experimental proof of heliocentrism.

There are a few theories about its formation and We will try to learn the most important ones in this lesson.

According the the “Nebular Hypothesis” surfaced and developed in the 18th century by Emanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace the Sun and the solar system formation and evolution began 4.6 billion years ago with gravitational collapse of small part of a Giant Molecular Cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids and other small solar system bodies formed.

The Molecular cloud was estimated to be about 65 Light years across. It was estimated that a supernova explosion of a star nearby generated shock ways travelling in the galaxy at super high speeds zipped passed through the molecular cloud which lead to shake and disturbance in the molecular cloud. As the cloud started spinning which initiated its collaping which in turn resulted in faster spin and so on. The collapse of the nebula condensed the atoms within it began to collide with increasing frequency, converting their kinetic energy into heat. the centre where most of th mass collected, became increasingly hotter than the surrounding disc. For thousand of Yeats the competing forces of gravity, gas pressure, magnetic fields, and rotation caused the contracting nebula to flatten into a spinning protoplanetary disc with a disc of about 200 AU and form a hot, dense protostar (a star in which hydrogen fusion has not yet begun) at the centre. With the gravitation force acting towards the centre of the protostar, the centre experience extreme heat and pressure resulting in fusion of hydrogen atoms into helium. It released enough electromagnetic radiation to illuminate the system of planets which were still in the formation. And this way “A Star Was Born”.

As per certain observations, it is believed that the initial cloud was spread across several light years and it gave birth for many stars in the close vicinity and our Sun is just one of the many. Like a typical molecular cloud, it mostly consisted if hydrogen with some amount of helium and small amounts of heavier emoluments fused by previous generations of stars. A similar such system we observe today is “The great nebula in Orion” located in the constellation of Orion. Observing that nebula gives us a great insight into formation of our solar system and also about the conditions before it created.