The carrina nebula is described as a star nursery. How are stars formed from that gas and dust?
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Stars are formed from massive clouds of dust and gas in space. Gravity pulls the dust and gas together to form a protostar.
As the gases come together, they get hot.
A star forms when it is hot enough for nuclear reactions to start.
Well, generally what happens is that there is a large nebula, a massive cloud of mostly hydrogen. Gravity begins to pull it together into one more massive ball, but due to properties of physics such as the laws of conservation of energy, some of the gas and dust begins to orbit around this ball, forming an accretion disk that also has some balls of matter forming, which would soon be planets.Anyways, over time as more matter is pulled in, the ball becomes bigger and bigger, which adds to gravity making it constantly pull more and more in.
But here is the catch, pulling stuff in like this generates a lot of heat, and the gravity generates a lot of pressure in the center.
The pressure pushes the atoms of hydrogen together to become closer and closer, the heat speeds them up on a molecular level, meaning they move faster and faster as atoms individually.The thing about atoms is that the nuclei of different atoms rarely ever touch, because the nuclei are both positive charges and like charges repel.
But eventually, the pressure becomes so immense and the heat begins to move the atoms around so much that at some point, the nuclei get close enough to each other and undergo a process known as fusion (basically, if the nuclei of atoms get close enough together, depending on the type of nuclei, then another force, the strong force as it is called, brings them together, this releases energy).
This releases heat, which heats up the core of the soon to be star more, which causes more fusion, which causes more heat, and so on in a chain reaction like this, and very quickly the star lights up, in what could be called an explosion.
This explosion also pushes out much of the random dust flying around in the accretion disk, only leaving the bigger ones, the planets.And a new star is born that will continue fusion for millions, billions, or trillions of years.
Stars are just big balls of hydrogen and other gases that are so massive that they crush themselves under their own gravity. Crushing themselves increases pressure and if that ball grows massive enough the pressure will grow to be big enough to facilitate nuclear fusion. At which point fusion begins and the whole thing starts to continuously explode and now you have a star. Nebulas are big balls of gas, but gravity hasn’t pulled them together enough to start fusion. It will take a few million years for gravity to do its thing, but when it does either a star will be born, or it wont be massive enough and you get a big ball of gas like Jupiter.
It is referred to this way because gravity attracts the local gas and dust and it grows until it has enough mass for fusion to ignite the core and prevent further inward collapse. This ignition or star birth can further condense other regions of gas and dust and they so too ignite as the chain reactions continue for eons as however many light years away it is in space it is as many years back in time.
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