subgiantn.
/ˈsʌbdʒʌɪənt/, U.S. /ˈsəbˌdʒaɪənt/ Astronomy.
An evolved star which lies above the main sequence and below the giants on the Hertzsprung–Russell diagram, being less luminous than giant stars of the same temperature or spectral class. Cf. giant n. 2c, subdwarf n. 2.
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subgiant1928
1928 B. W. Sitterly in Pop. Astron. 36 298 The other's [sc. star's] combination of type, mass, density, and surface brightness is very unusual. It might perhaps be called a ‘sub-giant’.
1941 Proc. Amer. Philos. Soc. 84 575 Totally eclipsed in the deep minimum by a less luminous subgiant exhibiting gG2 characteristics.
1962 New Scientist 3 May 217/1 There are several groups that are not on the main sequence... Prominent among these are the yellow and red giants like Capella and Arcturus (together with distinct groups christened subgiants and supergiants).
2007 Science 8 June 1420/2 As A stars age, they evolve into ‘retired A stars’, expanded subgiants with cooler temperatures and slower spins.
This entry has been updated (OED Third Edition, June 2012; most recently modified version published online March 2022).
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n.1928