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Name: Kathryn
Status: student
Age: 12
Location: N/A
Country: N/A
Date: 1999 - 2000

I'm doing a research project on space for my 1st hour science class. My question is: Why is there some space matter with atmospheres some without atmospheres some with life some without life some that are hot and some that are cold. How did these different features happen to different objects in space?

Objects very close to a star will get so hot that all the gases we normally think of as making up an atmosphere expand into such a large volume that they are hardly held in by the object's gravity. The light from the star has enough pressure to blow the atmosphere away from such objects. However, objects near stars that can't hold onto oxygen and nitrogen might still have atmospheres of some other element that is a gas at the object's temperature.

Small objects have so little gravity that they don't have to get very hot for this to happen.

Objects that are very very cold have no atmosphere because nothing remains a gas at their temperature. Comets, for example, have no atmosphere until they get near a star. Then their frozen gases thaw, and immediately get blown away by the star. We see this as a tail pointing away from the star.

Objects near stars are hot. Objects far away are cold unless they have some internal source of heat. A star has an internal source of heat (stars are basically nuclear reactors). Objects more than around ten times the mass of Jupiter become stars as they pull themselves together and the pressure in their middle rises to the point that little atoms fuse together into larger atoms. This releases enormous amounts of energy.

Tim Mooney

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