by%20Amanda%20Loo%20

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COSMOS 2005 Cluster 7 Presents
Globular Clusters

• by Amanda Loo
• Catherine Russell

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Outline

• What is a globular cluster?
• How do stars evolve?
• Observing
• Filters, tri-color image
• Age of and Distance to M13
• Age of the Universe

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What is a globular cluster?

• A globular cluster is a
• very dense
• extremely old
• super bright
• gravitationally bound
• populated (millions of stars)
• collection of stars found in the halo of our
  galaxy.

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Hertzsprung-Russell Diagrams
Bright
Luminosity
SUN
Temperature
Dim
Cold
Hot
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Asymptotic Giant Branch
Helium Flash
Red Giant Branch
The Giants
Horizontal Branch
Evolution of a 1 Solar Mass Star
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Observing

• M13 and M5
• Nickel 40 Inch Reflector Telescope at Lick
  Observatory on Mt. Hamilton
• Remote observing through video conference with
  Ellie Gates
• Digital detector called a charge coupled device
  (CCD)
• CCDs can detect photons but not color so we used
  filters to detect photons of different
  wavelengths.

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RGBs
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• Color Magnitude Diagrams
• Specialized H-R Diagram
• Converts luminosity to apparent
• magnitude (how bright it looks)
• Converts temperature to color
• (like heating a stove)

Helium Flash
Bright
Bright
Red Giant Branch
Magnitude
Horizontal Branch
Luminosity
Turnoff from Main Sequence
Dim
Dim
Hot
Cold
Color
Bluer
Redder
Temperature
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Yale Isochrones
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Isochrones

• Used to find age and distance
• Difficult to use
• Horizontal Branch not modeled

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Conclusions

• By fitting isochrones, we determined M13 to be 19
  billion years old!
• Literature says 14 billion- the same age as the
  universe.
• We also determined M13 to be between 4-10
  thousand light years away.
• Literature says about 24,000 light years.

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Thanks to

• Kirsten Howley
• Andrea Michels
• Becca, Molly, Jared
• open clusters group
• Ellie Gates
• Hilary Greg OBryan
• supplying teenagers with liquid nitrogen
• Jason Porter
• John Martin
• Kathy Cooksey
• Laura Chomiuk
• Malika Mountawakkil-Bell
• Monica Piñon
• for powerpoint tips
• Nick Konidaris Jay Strader
• balloon blower uppers computer donor
• CfAO
• COSMOS