The Formation of Stars

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The Formation of Stars
Where do they come from? How do they form?
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Star Formation

• Last weekstellar evolution. What happens after
  the main sequence. (Will return to shortly)
• Now, how to stars form? What do they form from?
  Space seems to be empty. Where does the material
  come from?

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Space isnt really empty

• Stars move in a dilute atmosphere called the
  interstellar medium.
• Typical density of 10-100 atoms/cc
• Compare with density of 4E19 atoms/cc in the
  Earths atmosphere
• Compare with 1024 atoms/cc mean density for Sun.

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Putting together the pieces in the puzzle

• To see how stars form, look at places where there
  are young stars.
• When we see massive main sequence stars (spectral
  class O), we know they are young.
• With fairly simple observations, we can find
  groups of O and B stars (OB associations)

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Young star clusters (the Rosette Nebula and Chi
h Persei)
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The primary example The Orion Nebula
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Fact that stars form in star clusters means the
Sun has siblings out there
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Stars form in the presence of dark clouds
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Dark clouds due to particulate matter

• Small particle absorb and scatter light
• Demo
• Particles primarily formed of carbon, silicates
• Most of matter which forms stars must be elsewhere

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Where the gas is molecular and very cold

• Discovery was a contribution of radio astronomy
• Utilized observations of rotational transitions
  of molecules

Emission from molecules Like CO, water,
ammonia Made with radio telescopes
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The sky in the glow of the carbon monoxide
molecule
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How do stars form from thesemolecular clouds?
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A Star is born.
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A Star is born (Part 2)
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What a new star (protostar) looks like. We can
study nearby examples in Taurus
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Molecular Clouds as Chemistry Sets in the Sky

• Number of molecules discovered in molecular
  clouds 152
• 8 species with 10 or more atoms
• Deuterated species overrepresented

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The future of molecular cloud studiesALMA

• 64 antenna interferometer
• 2010 August, first science
• 2012 December, full science operations

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ALMA