Lecture 31 Formation of Stars

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Lecture 31Formation of Stars
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Birth of Stars

• Stars originally condense out of a cold,
  interstellar cloud
• composed of H and He trace elements.
• cloud breaks into clumps (gravity)
• Each clump will make a star.

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Eagle Nebula -- HST
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• Proto-star Forms
• inner part of fragment becomes Proto-star
  continues to grow as mass falls on it
• gas falling onto it
• density and temperature increase
• center 1,000,000 K
• gravity gt outward pressure of the heat.
• Pre-main sequence star on the HR-diagram

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• Proto-star
• shrinks
• becomes hotter
• less luminous
• Proto-star begins fusion
• high temperatures and pressures in core
• Now a true star
• Can take 105 - 107 years
• Star moves to Main Sequence
• hydrostatic equilibrium

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LL Orionis
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Star Clusters

• Groups of stars form and condense in part of the
  cloud
• All types of stars form
• More M than O type stars form

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• O and B stars give off huge stellar winds
• Push gas away in a shock wave
• Compresses nearby gas

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• New stars are now outside of nebula.
• Stars form in compressed area
• Cluster may loosen up

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Eagle Nebula -- HST
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Star Forming Nebula
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Proto-planetary Disks (Orion Nebula) -- HST
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