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NOTES:
Spectral Class (Color-Temperature Class):
Annie Jump Cannon (1912) classified dark lines for 200,000 stars!
OBAFGKM
<----------------T
BLUE
RED
Subclasses: Sun is a G2V star.
A. 1-10 Spectral Subclass.
B. Luminosity Class I-V (I--supergiant, V--main sequence).
The Evolution of a Star:
Hertzsprung-Russell Diagram (1910): A plot of Luminosity vs
Surface Temperature, T (see overlay). A one solar mass star like
the sun goes through the stages of: protostar, main sequence,
red giant, planetary nebula, white dwarf.
Spectral Class (Color-Temperature Class):
Annie Jump Cannon (1912) classified dark lines
for 200,000 stars!
OBAFGKM
Pnemonic: Oh Be A Fine Geek, Kiss Me
RED
<-----------------T
BLUE
Subclasses: Sun is a G2V star.
A. 1-10 Spectral Subclass.
B. Luminosity Class I-V (I--supergiant, V--main sequence).
Nearby stars can be plotted-Luminosity vs Surface Temperature, T:
The more stars we plot, the more we see patterns. HR Diagram:
The majority of stars lie on the main sequence
of the H-R Diagram where they burn Hydrogen in their cores.
Arthur Eddington’s great discovery!
Mass determines stages of star life.
Analogy: weigh the baby at birth,
and know everything that
will happen to the baby.
He also proved stars bend light
Like Einstein’s theory suggests.
Also he suggested that star pressure balances gravity.
The outward pressure is created by heat and light.
The Hertzsprung-Russell, or H-R Diagram allows us
to plot the stages of life of stars from their initial mass.
Lifetime of a 1 solar mass star
Multiple Star Systems:
More than half have companions.
Most are: Binaries.
Optical double--a false binary
--two stars not bound together, one at a greater distance.
Albireo, an optical double. 10/25/03
Spectroscopic binary:
We don't see separate stars, just separate spectra
Eclipsing binary--one star eclipses another.
Two dips in the light curve.
Visual binary--actually seen as separate.
Castor in Gemini: a visual binary