ASTR250 S18 Classification
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Transcript of ASTR250 S18 Classification
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MgII means Mg+ or singly ionized, 1e-‐ missing
Annie Jump Cannon
Antonia Maury
Cecilia Payne-Gaposchkin
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Spectral Type
Ho@er Colder
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Zöllner’s (Incorrect) Hypothesis
Evolution Early-type Late-type
But the terminology stuck…
Subdivisions of Spectral Type:
Letter & Number
B0 hotter than B9
B0-B5 “early B”
B5–B9 “late B”
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Luminosity Class / Morgan-Keenan-Kellmann (MKK) Class
Class Description Ia-0 Hypergiant Ia Bright supergiant Iab Normal supergiant Ib Subluminous supergiant II Bright giants III Normal giants IV Subgiant V Main-sequence (dwarf) star
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V
III
I
Brown Dwarfs (only burn 2H NOT pp chain)