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Our galaxy contains at least 200 billion stars. 
Yet the details of how they formed remain mysterious.

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Scientists know that stars form from 
the collapse of huge hydrogen clouds...

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...that are squeezed under gravity 
until nuclear fusion ignites.

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But only about 30 percent of the cloud’s gas 
ends up in the newborn star. 

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So, where does the rest of the hydrogen go?

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Astronomers had assumed that a forming star 
blows off gas through stellar winds and jets.

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These winds and jets should stop further growth of the star.

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They should also create cavities in the surrounding 
gas that widen until the cloud dissipates.

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But a new study shows something different.

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Using observations from NASA’s 
Hubble and Spitzer space telescopes 
and ESA’s Herschel Space Observatory... 

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...researchers studied 304 developing stars 
in a region called the Orion Complex.

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They found that the cavities around the stars 
did not grow over time, as expected. 

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In fact, the cavities don’t seem to expand
until the stars push out all of the gas in the cloud. 

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If stars don't end up isolated in cavities, 
why doesn't the gas find its way into the star?

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For now, the answer remains a mystery.

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[ SILENCE ]