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ASTA02H3 Lecture Notes - Apparent Magnitude, Brown Dwarf, White Dwarf

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Parandis Khavari

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Astronomy Session 5
HR Diagram
luminosity (L) versus temperature (T) plot
two factors: size and temperature
learn how to plot a HR Diagram
note that temperature increases from right to left
white dwarves
main sequence
super giants
white dwarves
very hot
very small
very dense
almost as heavy as the Sun
of the Sun
ex. Sirius B
main sequence stars
make up a majority of the stars seen in the sky
source of energy for 90% of the stars (on the graph)
burn Hydrogen into Helium
majority of a stars life is spent in main sequence
longest period of a star’s life
red dwarves
small luminosity and radii
bottom right of the area main sequence stars occupy
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super giants and giants
large stars
huge radii
brown dwarves
not stars
spectral class
eight main categories of stars
O, B, A, F, G, K, M, N
each divided by a subclass
ranges from zero to nine
does not provide numerical descriptions
luminosity-mass relationship
only applies to main sequence stars
L ∝ R2T4
correlates with the spectral class
O, B, A, F, G, K, M, N
R2 refers to the size or the radius of a star
T4 refers to the surface temperature of a star
luminosity-mass relationship equation variation
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