Star Formation (Star Birth)
Star formation is a simple but long process. It depends almost entirely on one thing: gravity. In outer space, things are always coming together because of gravity. As objects group-up, their gravity gets even stronger. If there’s enough matter around, it all might cluster up into a small area, creating what’s known as a protostar. This young star will then keep growing until it reaches the main sequence.
The Stages of Star Formation
Several things can cause it to do so, generating a strong center of gravity. Often times, a supernova will throw matter into a nebula, pushing things together. Or, perhaps, two nebulae might come together to form a very dense cloud.
In one giant blast, most of the collapsing gas gets thrown back outwards. In the center of the blast is a newly formed protostar! What’d happened was that some of the gas got so dense, it formed this new star. Then, like any star would, it pushed back on any leftover gas trying to crush it.
Protostar to Main Sequence Star
Even so, we still can’t call them real stars. They’re very unstable and continue to undergo rapid change as they get ready for the main sequence. So instead, we call them pre-main-sequence stars. It’s only once a pre-main-sequence star settles down that we finally have a fully grown star.
The Possibility of Planets Forming
It’s important to note that much of the cloud which built up a star will remain around it after formation. What’s more, stars tend to attract large bodies of metal or rock. All of this matter can start to clump together in the same way that a protostar does. Rock and metals will build-up strong, dense planets (like Earth) while remaining gases will contribute to gas giants (like Jupiter).
Other Great Resources:
The ESA on Star Birth: https://www.esa.int/esaKIDSen/SEMY06WJD1E_OurUniverse_0.html
More Facts on Star Formation: https://www.ouruniverseforkids.com/how-stars-are-born/
Cosmos4Kids on the Development of Stars: http://www.cosmos4kids.com/files/stars_develop.html
(Video) A Star is Born: https://www.youtube.com/watch?v=mkktE_fs4NA