At some point a star or shockwave will move through the nebula and pull all the ingredients together. This event is like the craving one sometimes develops to bake chocolate chip cookies. Once all the ingredients have come together and the conditions are right (the oven is preheated), then the universe uses gravitational collapse as one would use one’s hands to pack all the ingredients together tightly and to mix them correctly. Gravitational collapse kneads the dough into balls for ten thousand to one million years. During this time, the star dough cools itself by emitting radio waves and infrared radiation; however, the gravitational collapse will continue to heat the star dough despite the dough’s attempts to cool off. This is due to the continual contraction of the star dough, which increases the heat. The radio waves and radiation shooting off the star dough can be thought of as the water which bakes out of the cookie dough.
While gravitational collapse happens, the star dough will spin with increasing speed, flattening the ball of star dough, just as a cookie will flatten out during baking. At this point the chocolate chips will become visible. At the center of the flattened star dough will be the largest chunk of chocolate: the protostar. The other chocolate chips will orbit the protostar; these chocolate chips are called “protoplanets.” This stage is also called “Pre-main Sequence” (“Stellar Birth,” CWRU). If the dough has enough of the right ingredients, then the protoplanets and the protostar will continue to undergo gravitational collapse for about 50 million years until the internal temperature of the protostar reaches about 18 million degrees Fahrenheit (~10 million Kelvin) (“Stellar Birth,” CWRU). At this point, hydrogen fusion will begin, and the protostar will become an actual, stable Main Sequence star (“Stellar birth,” CWRU). The solar wind will blow away any remaining nebula dust around the star. One might note that since there is no air in the vacuum of space, that “Solar wind” is a misnomer, but that does not stop these charged particles from shooting out of the new star at speeds exceeding “1.5 million kph” (“Glossary”, CWRU). At this point, the star dough has become a solar system cookie. This cookie will last for anywhere between 5 and 10 billion years, until the star explodes. (A good chef will avoid such an outcome with their cookies.)
If the dough does not have enough ingredients, then the protostar will become a brown dwarf. A brown dwarf is a failed star and, much like a chocolate chip cookie which is lacking some ingredients, is little more than a hot, useless lump. The surface temperature of a brown dwarf is about 1800 Kelvin which is roughly one one-thousandth of the heat needed to create an actual star. Some scientists blame brown dwarfs for the missing mass of the universe. This missing mass, also called “dark matter,” claims almost 25% of the weight of the universe (“Stellar Birth,” CWRU). It is important to note this rather encouraging news, because if one’s chocolate chip cookies turn out right more than 75% of the time (with respect to mass), then one can count oneself as being better than the universe at making cookies.
"Glossary." Journey through the Galaxy. Case Western Reserve University, 11 Jan. 2006. Web. 27 Jan. 2011.
"Stellar Birth." Journey through the Galaxy. Case Western Reserve University, 11 Jan. 2006. Web. 27 Jan. 2011.