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A Star is Born
The scientists who study the universe and its origins have evidence that the universe began between 13 and 15 billion years ago. Scientists theorize that within tens of minutes after the beginning of the universe, space contained hydrogen widely spread out. After a few million years clumps of hydrogen began to develop. Gravitational attraction continued to work to pull the hydrogen even closer together. Eventually the hydrogen began to clump into clouds of gas. As large masses of hydrogen got closer together, gravitational attraction compressed the hydrogen more and more. If the mass was at least half as much as our Sun, then the hydrogen became so compressed and hot that nuclear fusion began, and the new star gave off heat, light, and charged particles. This is a simple story of star birth. A more complete story is contained in the article "We are All Star Stuff" by Neil F. Comins and in History of the Universe.
About 5 billion years ago the Sun also formed out of clumps of material in space. In the case of our Sun this material came from the remains of older stars that lived out their life cycles, converting some of their hydrogen fuel into all of the other elements of the Periodic Table.
The Hubble Space Telescope has provided us with clear images of stellar nurseries, notably the Eagle Nebula, in which stars are being born.
Click on image to enlarge.
The material was made of gas and dust at very low densities. Again, gravitational attraction caused the matter to contract and rotate faster. Shock waves from the explosion of a nearby star may have accelerated the process. Increased density resulted in increased contraction and more matter was attracted to the location of our developing star. The rate of rotation also increased due to conservation of angular momentum. The roughly spherical cloud flattened into a disk with a fat center. The center contained most of the gas and dust. The outer regions of the disk clumped together forming the planets. At some point the contraction of the center developed such intense pressure that nuclear fusion reactions were started and "A Star Is Born". The concept of the Sun as a spinning nuclear fusion furnace seems to be a reliable foundation for our research. However, other details of The Amazing Structure of the Sun are important to understanding our closest star and how it affects Earth.
For a simple explanation of the birth of a solar system is available on-line from NASA's Observatorium. For more detail visit Zoom Astronomy
- NASA Official: Dr. James Thieman
- Project Manager: Don Robinson-Boonstra
- Website Manager: Bryan Stephenson