Lecture at Aug 7

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Astronomy & Astrophysics
Marija Stankovic

Star Formation • Stars do not live forever. They are “born” and they “die” • Depends on its mass Mass influences the evolution of the star • • Where are stars born? • Space between stars is not empty • Interstellar media full of gas and dust • The density of the medium has few particles • The interstellar medium is filled with microscopic dust particles and gas • Dust grains scatter and absorb virtually all visible light that enters a cloud preventing us from seeing what lies behind it • In infrared we can see past the dust and see that behind dark regions there are lots of stars Any longer wavelength will go over that dust • • Short wavelength ligh will not pass but longer will Star nurseries • Orion constellation • Orion nebula in visible light • Colours added later and correspond to emission of different spectral lines • In infrared light we see that a very young cluster is embedded in the gas • In such nebulae, we tend to find lots of dark patches, which are places where the gas and dust are concentrated enough that they block out background light • Sometimes happens spontaneously but most likely triggered by some kind of shockwave or collision • Often these dark dusty structures are studded with young stars • Where stars are formed • These regions called molecular clouds • Usually these nebular are rich in molecules, often quite complex ones • They are called molecular clouds • If you have dust clouds that block light, then inside thick dust clouds there should be no light at all Gravity vs Pressure • Stars and other interstellar material are in a perpetual battle between forces puling in (gravity) and forces pushing out (pressure) • Gravitational equilibrium • This happens in every star • Also happens in interstellar clouds • Molecular clouds are cold (10-30k) • Cold cloud - > molecules move slowly - > no outward pressure • Pressure decreases because of slow movement • Gravity wins! Clouds begin to contract • Fragmentation of a cloud • This simulation begins with a turbulent cloud containing 50 solar masses of gas
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