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physical object > natural object > celestial body > star > subdwarf

subdwarf (sd)
subject			fact

subdwarf	has symbol sd
	has luminosity class VI
	has definition A metal-poor main-sequence star. On the H-R diagram, subdwarfs lie slightly below the metal-rich Main Sequence, because they are fainter than metal-rich main-sequence stars of the same color.
	has definition Star whose luminosity is 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. Subdwarfs are primarily Population II and lie just below the Main Sequence on the H-R diagram.
	has definition Late-type object whose observed color and absolute magnitude place it below the Main Sequence.
	is a kind of star
star	has star surface temperature
	has spectral type
	has V magnitude
	has B magnitude
	has U magnitude
	has position on celestial sphere from the point of view of Earth
	has parallax from the point of view of Earth's orbit
	has proper motion
	has radiation at surface which is diffused out from the hotter core
	has energy source gravitational contraction and or fusion
	has energy production which takes place primarily within the core
	has surface density which depends on luminosity class
	has surface temperature greater than 1000 Kelvin
	has apparent magnitude
	has absolute magnitude
	has age
	has catalog star catalog
	has material hydrogen, helium
	has velocity determined from proper motion and radial velocity
	has mass greater than 0.08 the sun's mass
celestial body	has spectra
physical object	has location or center of gravity
	has angular momentum
	has momentum
	has temperature
	has volume
	has extent

Kinds of subdwarf :

• Kapteyn's star (10 facts) (HD 33793, CD -45 1841) - A nearby high-velocity M0 subdwarf that is both the nearest halo star to the Sun and the nearest star that orbits the Galaxy backward.
• sdB (3 facts) - Subdwarf B star with very broad and shallow Balmer lines; fewer lines of the Balmer series are visible than for normal dwarfs.
• sdO (3 facts) - Subdwarf O star showing few very broad and shallow Balmer lines and a very strong He II 4686 line.

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