Page 54 - Curriculum Visions Dynamic Book

resulting from our Sun sweeping very close to another star. The intense gravity would pull material away from the stars and form a disk, which would later begin to form into planets. But observations show that near-star events are very rare.
Modern ideas
Many of these early ideas were based on the belief
that stars contained solid materials. But then it was discovered that they are, in fact, balls of gas. So some means of getting the material to condense into planets was then required.
Moreover, it became clear that stars (including the Sun) form inside clouds of gas and dust rather than create them. So, scientists began to look for a way that the planets and the stars could have been made at the same time.
Today, many scientists think that the Solar System began as a cloud of gas and dust (a supernova) that started to collapse inward on itself as it moved through a spiral arm of the galaxy.
As this happened, the cloud became denser. Because the gravity of the galaxy would affect the cloud differently on the side nearest the center of the galaxy than on the side away from it, gravity would start to make the collapsing cloud rotate. At the same time, it would flatten into a disk. This is called the solar nebula. It would have looked like a tiny galaxy with spiral arms containing more concentrated regions of dust and gas.
As the dust and gas were pulled to the center of the nebula, they spun faster and heated up. At the center of this spiral speeds and temperatures got great enough for nuclear reactions to take place and so create a star, in this case our Sun.
At the same time, planets began to grow in the outer arms of the spirals, much as Kant had originally suggested. The planets then began to influence one another, possibly changing their orbits as a result. Some early planets probably collided, shedding the
To make something more concentrated or compact.
false colour The colours used to make the appearance of some property more obvious.
nebula (pl. nebulae) Clouds of gas and dust that exist in the space between stars.
supernova A violently exploding star that becomes millions or even billions of times brighter than when it was younger and stable.
condense
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