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Subdwarf O Star
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 about 10 to 100 times that of the Sun, and have a mass approximately half that of the Sun. Their temperature ranges from 40,000 to 100,000 K. Ionized helium is prominent in their spectra. Their surface gravity (typically given as the gravity's logarithm), log ''g'' is usually between 4.0 and 6.5. Many sdO stars are moving at high velocity through the Milky Way and are found at high galactic latitudes. Structure The structure of a subdwarf O star is believed to be a carbon and oxygen core surrounded by a helium burning shell. The spectrum shows that the content is from 50 to 100% helium. History In the early 1970s Greenstein and Sargent measured temperatures and gravity strengths and were able to plot their correct position on the Hertzsprung-Russell diagram. The Palomar-Green survey, Hamburg surveys, Sloan Digital Sky Surv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subdwarf O Star Schematic Cross Section
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the stellar classification#Yerkes spectral classification, Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 Absolute magnitude, 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. 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". Since Gerard Kuiper, 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_subdwarf_anchor, Cool subdwarfs * #hot_subdwarf_anchor, Hot subdwarfs Like ordinary main sequence, main-sequence stars, cool subdwarfs (of spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
