Star of luminosity class VI under the Yerkes spectral classification system
Hertzsprung–Russell diagram
Spectral type
O
B
A
F
G
K
M
L
T
Brown dwarfs
White dwarfs
Red dwarfs
Subdwarfs
Main sequence ("dwarfs")
Subgiants
Giants
Red giants
Blue giants
Bright giants
Supergiants
Red supergiant
Hypergiants
absolute magni- tude (MV)
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. On a Hertzsprung–Russell diagram subdwarfs appear to lie below the main sequence.[a]
The term "subdwarf" was coined by Gerard Kuiper in 1939, to refer to a series of stars with anomalous spectra that were previously labeled as "intermediate white dwarfs".[1](p 87)
Since Kuiper coined the term, the subdwarf type has been extended to lower-mass stars than were known at the time. Astronomers have also discovered an entirely different group of blue-white subdwarfs, making two distinct categories:
Cool subdwarfs
Hot subdwarfs[a]
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of blue-white subdwarfs, making two distinct categories: Cool subdwarfs Hot subdwarfs Like ordinary main-sequence stars, cool subdwarfs (of spectral types G...
A B-type subdwarf (sdB) is a kind of subdwarf star with spectral type B. They differ from the typical subdwarf by being much hotter and brighter. They...
A subdwarf O star (sdO) is a type of hot, but low-mass star. O-type subdwarfs are much dimmer than regular O-type main-sequence stars, but with a brightness...
of low surface gravity, subdwarfs and unresolved binaries. The prefix sd stands for subdwarf and only includes cool subdwarfs. This prefix indicates a...
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Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence ("dwarfs") Subgiants Giants Red giants Blue giants Bright...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
of low surface gravity, subdwarfs and unresolved binaries. The prefix sd stands for subdwarf and only includes cool subdwarfs. This prefix indicates a...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
hypothetical stage in red dwarf interstellar evolution O-type subdwarf B-type subdwarf Blue star (disambiguation) Blue giant (disambiguation) This disambiguation...
1130 is a nearby pre-cataclysmic triple star system consisting of a cold subdwarf of spectral type sdM3 (A), an ultramassive white dwarf (B) and a cold brown...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence ("dwarfs") Subgiants Giants Red giants Blue giants Bright...
V391 Pegasi, also catalogued as HS 2201+2610, is a blue-white subdwarf star approximately 4,400 light-years away in the constellation of Pegasus. The star...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
the brightest known O class subdwarf stars. HD 49798 was discovered in 1964 to be a rare hydrogen-deficient O class subdwarf, and was the brightest known...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
evolution Protostar Young stellar object Pre-main-sequence Main sequence Subdwarfs Subgiants Giants Red / Blue Bright giants Supergiants Red / Blue Hypergiants...
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Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence ("dwarfs") Subgiants Giants Red giants Blue giants Bright...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence ("dwarfs") Subgiants Giants Red giants Blue giants Bright...
Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon...
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