Stars are born from nursery-like nebulaes
"How did the stars form?" asked Josh Mota, 10, a recent fifth-grade graduate from O'Plaine School in Gurnee.
A star is a ball of gas - hydrogen and helium. Gravity keeps the gas from escaping and gravity is what creates a star.
"Stars form from large clouds of gas floating in space," said Dr. Geza Gyuk, director of astronomy at the Adler Planetarium in Chicago. "These clouds, called nebulae, are sort of like nurseries for stars," Dr. Gyuk said.
Like rolling a snow ball into a huge boulder to create a snowman, stars develop when denser parts of the nebulae create a ball of dust and gas. Gravity causes the gas to become compact. The process repeats over and over and ultimately a star is born. Gravity continues to exert extreme pressure, but the roiling nuclear reactions within the star's core prevent gravity from causing the star to collapse.
"When the star is born it begins to shine and the gas and dust nearby are pushed away," Dr. Gyuk said.
How many stars are there? According to Dr. Gyuk, "A rough estimate shows that the observable universe contains thousands of millions of trillions of stars."
Stars have a life cycle. They are born and then they experience what astronomers call the main sequence. That's the point in the star life cycle when the star fuses hydrogen to helium and the pressure inside the star is in balance with gravity. Eventually, the hydrogen in the star's core is exhausted. That leads to the next phase - a red giant. Eventually, most stars use up all of their fuel. That leads to the final phase - a white dwarf.
p class="factboxheadblack">The Fox Lake District Library suggests these book titles on stars:
"Mysteries of deep space: Black holes, pulsars, and quasars," by Isaac Asimov
"Summer Stargazing," by Terence Dickinson
"The Star Guide," by Robin Kerrod
"Exploring Our Solar System," by Sally Ride
"Stars," by Paul P. Sipiera
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