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(sub-jÿ -ănt) A giant star of smaller size and lower luminosity than normal giants of the same spectral type, Alpha Crucis being an example. Subgiants form luminosity class IV, lying between the main-sequence stars and the giants on the Hertzsprung–Russell diagram.



a member of a group of cool stars located between the giants and the main sequence in the Hertzsprung-Russell diagram. By comparison to main sequence stars of the same luminosity, subgiants are larger and have lower surface temperatures. Most known examples of subgiants are found in eclipsing binary systems of the Algol type. Subgiants apparently represent a late stage in the development of binary stars.

References in periodicals archive ?
This indicates it may be a sub-giant (luminosity class IV).
Briefly, the more massive star evolves off the main sequence first, swelling in the sub-giant phase until it overflows its inner critical surface or Roche lobe, depositing the overflowed mass on the secondary.
The researchers concluded that the star is a few billion years older than the Sun and no longer burns hydrogen at its core, so has entered a sub-giant phase in which its radius is 60 percent greater than the Sun's.
Double stars, Cepheid variable stars, Viewing galaxies, Black holes, Main-sequence stars, Globular clusters, Discovery of Proxima, Extra-solar planets, Open star clusters, Sub-giant stars, Nebulae, Yellow-dwarf star, Barred spiral galaxies, Galaxies and time, Close double stars, Coloured double stars, Super galaxy clusters, Mira variable stars, Giant stars, Carbon stars, Observing double stars, Solar type stars, Nicolas Louis de Lacaille, Astrophotography, Light year, Sub-dwarf stars, Venial equinox, Hot Jupiters, Delta-Scuti variable star, Apparent brightness.
The Troyano Block is on trend with the sub-giant Orito field located 12 miles to the south.
It is wonderful that this tendency, intensifying at the bottom, gives the anomalously large luminosities for sub-giants (the satellites of Algol)--the circumstance, considered by Struve [30].