chapter 8 survey of solar systems

The solar system formed from a cloud of cold gas and dust called the solar nebula about 4.6 billion years ago Astronomers believe that the solar system formed from a vast cloud of interstellar gas and dust called the solar nebula. This cloud condensed 4.6 billion years ago under the influence of its own gravitational force to form our Sun, the planets, and the other bodies in the solar system. This is an image of one of these clouds (the Orion nebula) The stars in this cloud as formed from the gas in the cloud. Many Astronomers believe that the univers3e formed between 14-15 billion years ago in a violent event called the “Big Bang”. But during this event, only the lightest elements existed such as hydrogen, helium, and lithium. So the first stars that were formed only contained these light elements. But we know that there are elements much heavier than these that exist on Earth such as oxygen, silicon, aluminum, carbon, iron, etc. So when we come up with a theory for how our solar system was formed, we must take into consideration the existence of these heavy elements. Remember, the creation of our solar system is an entirely different event from the big bang. The big bang brought about the existence of our Universe, but the solar system was formed billions of years later. We now know that it was born in gas and dust that contained heavy elements. These elements were created from the birth and deaths of several generations of stars. We will later find out that stars live because they undergo nuclear reactions in their centers. The end states of these nuclear reactions are heavier elements. Which get ejected outwards when some stars explode as supernovae. Then eventually new stars are created out of the gas ejected from the stars that are exploded. And that is why we know that we were not created from the first generation of stars. Because of the existence of these heavier elements. Planets like the Earth, cannot exist until several billions of years after the Big Bang. This would give it enough time for stars to be born and die and new stars to be born and die and have planets with heavy elements. Sometimes the explosive force of a supernova compresses fragments of interstellar gas and dust clouds that had been ejected from earlier generations of stars. These fragments are pulled inward on themselves by mutual gravitation attraction of their gas and dust particles thereby creating new star and planetary systems. The collapsing matter is primarily hydrogen and helium, but the stars that ejected it had converted some of it into heavier elements. These include the building blocks of life and this is believed to be how the solar system formed- the debris leftover from a previous generation of stars. Shakespare line: we are the stuff that stars are made of.