Slide 1
Dense regions of gas and dust collapse under gravity
Stars form when dense regions of interstellar gas and dust collapse under gravity. Cold molecular clouds provide environments where this can occur.
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Cold gas has less thermal pressure resisting compression than hotter gas at the same density. A cloud’s structure also matters: dense cores within a larger region can evolve differently from their surroundings.
Slide 2
Contraction heats a protostar before sustained fusion
As a core contracts, gravitational energy is converted into heat. The developing object, called a protostar, can shine before sustained hydrogen fusion begins.
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Luminosity alone therefore does not identify the energy source. A young object powered largely by contraction differs physically from a main-sequence star supported by an established core fusion process.
Slide 3
Rotation gathers some material into a disk
Collapsing material usually carries angular momentum. Rather than falling directly inward from every direction, some gathers into a disk around the young object.
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The surrounding envelope and the disk are related but distinct structures. Observations of gas motion help researchers determine how material moves between them and toward the growing star.
Slide 4
Young systems can send material outward while gathering more
Young stellar systems can launch outflows and jets while material is also accreting. Star formation does not turn every part of a cloud into a star.
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Winds and radiation from young stars also affect nearby gas. This feedback can change the local supply of material and reshape the environment in which additional stars might form.
Slide 5
Infrared and radio reveal stages hidden by dust
Dust can obscure forming stars in visible light. Infrared and radio observations reveal material and motions that an ordinary photograph may miss.
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Researchers compare many objects at different stages because one formation process lasts far longer than a human observing career. The evolutionary account is assembled from observations, physical models and their agreement.
Sources
- Star Formation
OpenStax, Rice University
- Making a Stellar Baby
ESO