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physical object > natural object > celestial body > star > Population I star > Population I Cepheid > Eta Aquilae

Eta Aquilae
subject			fact

Eta Aquilae	has discovery date 1784
	is a part of Aquila
	has definition A pulsating star in the constellation Aquila. It was the first Cepheid discovered, in 1784.
	is an instance of Population I Cepheid
Population I Cepheid	has period 5-10 days
	has absolute magnitude <Mv> = -0.5 to -6
	has synonym classical Cepheid
	has synonym young disk Cepheid
Population I star	has author Baade (1944)
	is a part of disk
Cepheid	has prototype delta Cephei
	has spectral type F star, G star and K star
star	has star surface temperature
	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 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
variable	has name designated with R, S, T, U, V, W, X, Y, or Z and the genitive of the latin constellation name RR, RS, RT, RU, RV, RW, RX, RY, or RZ and the genitive of the latin constellation name when the single letter designations are exhausted AA...AZ, BB...BZ, etc. (omitting J), which ends with QQ...QZ and the genitive of the latin constellation namewhen the RR...RZ designations are exhausted V 335, V 336, etc., when the double letter designations are exhausted
	has observational problem some difficulty in distinguishing between various kinds
	has observable variation time scale within a period of decades
	has light curve
	has optical brightness variation 0.2 magnitudes or greater
	has amplitude
physical object	has location or center of gravity
	has angular momentum
	has momentum
	has temperature
	has volume
	has extent

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