Birth of a Star
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Transcript of Birth of a Star
Birth of a StarJenn R
and
Kim B
Interstellar Cloud
• an accumulation of gas, plasma and dust in our and other galaxies
• They are very high in density
Collapsing Cloud Fragment
• Cores of the molecular interstellar clouds become gravitationally unstable, fragment, and begin to collapse
• Shockwaves from supernovae or other energetic astronomical processes trigger star formation in nearby nebulae
Fragmentation Ceases
• When the density and temperature is high enough, deuterium fusion ignition occurs
• Outward pressure of the resultant radiation slows the collapse
• The accretion of material happens partially through a circumstellar disc
Protostar
• The material the cloud is made of continues to “rain” on the protostar which is an object that forms by contraction out of the gas of a giant molecular cloud
• In this stage bipolar flows are produces probably in effect of the angular momentum of the falling material
Protostar Evolution
• Hydrogen begins to fuse in the core of the star and the rest of the enveloping material is cleared away
• The protostar follows a Hayashi track which is the path in the HR Diagram after protostellar cloud has reached approximate hydrostatic equillibrium
• Once Hayashi limit is reached the contraction stops
• Stars with less than .5 solar mass then join the main sequence
Newborn Star
• Once the weight of the stars matter is balanced by radiation pressure it evolves to a stable state
• New stars come in a variety of sizes and colors
• They range from hot and blue to cool and red. The brightness and color depend on surface temperature, which depends on mass
– Mass ranges from .085 to 20 solar masses
Main Sequence
• A new star will fall at a certain point on the main sequence of the HR Diagram
• Cool red dwarfs burn slowly and remain on main sequence for billions of years
• Hot supergiants leave the main sequence after only a few million years
• After a star burns most of the hydrogen in its core it moves off the main sequence
• The amount of energy generated at the dense core region when hydrogen fuses into helium determines where it is on the main sequence
Works Cited
• www.wikipedia.org
• http://www.harvard.edu/COMPLETE/learn/star_and_planet_formation.html