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Yellow supergiants generally have spectral types of F and G, although sometimes late A or early K stars are included. [1] [2] [3] These spectral types are characterised by hydrogen lines that are very strong in class A, weakening through F and G until they are very weak or absent in class K. Calcium H and K lines are present in late A spectra, but stronger in class F, and strongest in class G ...
Rigel, the brightest star in the constellation Orion is a typical blue-white supergiant; the three stars of Orion's Belt are all blue supergiants; Deneb is the brightest star in Cygnus, another blue supergiant; and Delta Cephei (itself the prototype) and Polaris are Cepheid variables and yellow supergiants.
Type I Cepheid variables, more luminous still and mostly supergiants, with even longer periods; Delta Scuti variables, includes subgiant and main-sequence stars. Yellow giants may be moderate-mass stars evolving for the first time towards the red-giant branch, or they may be more evolved stars on the horizontal branch.
Intrinsic variable types in the Hertzsprung–Russell diagram showing the Yellow Hypergiants above (i.e. more luminous than) the Cepheid instability strip. A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass.
Alpha Leporis has a stellar classification of F0 Ib, [4] with the Ib luminosity class indicating that it is a lower luminosity yellow supergiant star. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. [20]
Artist's illustration of Wezen, a yellow supergiant 1,600 light-years away in the Canis Major constellation. Delta Canis Majoris is a supergiant of class F8. Its surface temperature is around 5,818 K, [12] and it is 14 to 15 times more massive than the Sun. Its absolute magnitude is −6.77, [8] and it lies around 1,600 light-years away. It is ...
The primary component of the φ Cassiopeiae system is a very luminous yellow supergiant. Its absolute magnitude is comparable to some yellow hypergiants but it does not show the level of mass loss and instability that would qualify it as a hypergiant itself.
One astrophysical method used to definitively identify yellow hypergiants is the so-called Keenan-Smolinski criterion. Here all absorption lines should be strongly broadened, beyond those expected of bright supergiant stars, and also show strong evidence of significant mass loss.