M 39
M39 is a large cluster of stars about 800 light years away. It is between 230 and 300 million years old.
What are Stars?
The universe was created about 15 billion years ago with the "big bang," a cosmic explosion that resulted in an expanding cloud of hydrogen and helium gas. Where there were higher concentrations of these gases, the gravitational attractions of the gas molecules led to the growth of the first generation of stars. As more and more material fell into each new star, the rising pressure at its center finally became high enough to start the process of nuclear fusion, in which the nuclei of hydrogen and helium merge to form heavier elements. This was accompanied by the release of energy, which made the star begin to shine. Therefore, a star is a large ball of gas that creates and emits its own radiation.
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M39 is a large cluster of stars about 800 light years away. It is between 230 and 300 million years old. |
Our Sun belongs to a generation of stars created 4.6 billion years ago, when our galaxy was roughly half its present age. A cloud of interstellar gas and dust collapsed to form the nebula from which the Sun and the rest of our solar system grew.
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Another of NASA's Small Explorers, the Transition Region and Coronal Explorer (TRACE), took this photograph of the Sun. |
Last Updated: 1/3/99
