Transcript Globular Clusters - Lick Observatory

Vintage Stars
Doris Michue, Edgar Navarro,
Lucy Rodriguez, Tony Trieu
What is a Globular Cluster?
Types of Telescopes
Credited to Kathy Cooksey
Sensitivity
•Telescope size doubled from left to right.
Credited to Astrometry
The 40” Nickel Telescope
At Lick observatory outside
San Jose.
We however observed remotely.
Elinor Gates helped us observe.
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We took pictures with three different filters because CCD are color
blind so we make them see color by using as filter.
We took a long exposure to see faint stars and short exposure so we
wouldn’t over saturate the picture.
CCDs
Very important in the field of astronomy.
Used to collect light in a field array of pixels
.
CCDs are not perfect:
1. Cosmic rays
2. Hot pixels
3. Saturation
4. Low Charge Transfer Efficiency (CTE)
5. Read noise
6. Bias
7. Dead Pixel
8. Variable Quantum Efficiency (QE)
9. Dust Donuts
http://www.watch.impress.co.jp/av/docs/20030729/ccd.jpg
http://www.1394imaging.com/img/cameras/ccd.en.gif
Data Reduction
Two main elements to reducing data from raw images:
1. Using Biases to remove charge permanently stuck in
CCD
2. Using Flat Fields to clean up dust donuts
Bias Image
Elinor Gates, Lick Observatory; 40” Nickel Telescope
…into this!
Turns this...
Flat Field
Elinor Gates, Lick Observatory; 40” Nickel Telescope
Elinor Gates, Edgar Navarro; Lick Observatory; 40”
Nickel Telescope
Edgar Navarro
Picking and Choosing
We have a big pile of stars, now what?
•Picking PSF (Point Spread Function Stars)
•Defining what a star looks like
•Determine brightness and color of each star
Edgar Navarro
Image prior to photometry
Why are these two different?
Edgar Navarro
Image after photometry
Edgar Navarro
Low Mass Stars
• Range from eight hundredths to eight times the mass of the sun
• Stay on main sequence for billions of years
• Fuse hydrogen for most of star’s life
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http://imagine.gsfc.nasa.gov/docs/teachers/lessons/xray_spectra/images/life_cycles.jpg
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Death of Low Mass Stars
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Helium fusion ceases
Core collapses
Poof!
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http://universe-review.ca/I08-09-planetarynebula2.jpg
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Color Magnitude Diagrams
• Plots the magnitude
and color of stars in
our cluster.
• All stars plotted are
Red Giants and
Helium Burning stars.
Isochrones

Generated by a computer
which creates a simulation of
the aging of stars of different
masses.
 A freeze frame CMD (color
magnitude diagram) of a group
of stars with the same age.
 Can be used to determine the
age and distance of a star
cluster.
Credited to: Scott Seagroves
Finding Age
Finding Distance
Finding Distance
By using this equation: d = 10 0.2 (m - M+ 5+ Ar)
We can find the distance to our cluster.
d= distance [in parsecs]
M=absolute magnitude [the actual brightness]
m=apparent [how bright the star appears to us]
Ar=Extinction [amount of dust in-between us and our cluster]
Globular Cluster M13
13 Gyr 26,500 Lyr
(About the age of our universe.)
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Globular Cluster M12
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CMD
Age: ~11 Gyrs old (11 billion)
Distance: 5,000 parsecs (equivalent to 16,300 light years)
M5
Edgar Navarro
Isochrone fitted on top of a CMD (ColorMagnitude Diagram) diagram
Distance: ~11,000 pc = ~35,860 ly
This distance is about 2.7 million billion times
the diameter of the earth.
3 Color image of M5 Globular Cluster
Age: ~ 15 Billion years old
M92
Distance: 31700, LY
Age: 17 Gyr
Summary
•Globular Clusters + Telescopes
•CCDs + Data Reduction
•Stellar Evolution of Low Mass Stars
•Isochrones and CMD Diagrams
•Individual Galaxies
Acknowledgements
University of California Observatories - Lick Observatories, Elinor Gates
The CfAO
Kathy, John and Gene
Emily and Laura
Cosmos Staff
Vay and Daisy
… And thanks to all the stars …