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physical object > natural object > celestial body > star > metal-poor star > horizontal branch star

horizontal branch star
subject			fact

horizontal branch star	has color blue to yellow
	has location on H-R diagram extends shortward from the asymptotic branch at an approximately constant absolute bolometric magnitude of about 0.3
	has definition A metal-poor star after it has undergone the helium flash and begins to quietly burn helium into carbon and oxygen in its core and hydrogen in a surrounding envelope.
	is a kind of metal-poor star
metal-poor star	has metallic line strength weak
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 horizontal branch star :

• RR Lyrae star (4 kinds, 18 facts) (cluster variable, cluster variable) - Periodic variable with period less than one day, and of spectral types A to early F., Type of short-period variable stars. Spectrally classified as A to F giants. They were once called cluster-cepheids., A large class of pulsating (amplitude variation about 1 mag) blue giants of anomalous spectral type (A2-F6) with periods of less than 1 day. Their average absolute magnitude is about +0.8. which makes them almost 50 times more luminous than the Sun. They are Population II objects often (but not always) present in globular clusters. RR Lyrae stars are valid distance indicators out to more than 200 kpc.

Up: metal-poor star