Question:
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?
Replies:
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.
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