An Etymological Dictionary of Astronomy and Astrophysics

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فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک

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yellow hypergiant (YHG)
  هیپرغول ِ زرد  
hiperqul-e zard
Fr.: hypergéante jaune  

An evolved, → very massive star of spectral type F or G with a very high luminosity (~105 times solar) lying near the empirical upper luminosity boundary in the → H-R diagram (→ Humphreys-Davidson limit). Yellow hypergiants have high → mass loss rates (10-5-10-3 solar masses per year) and are in a short, transitional evolutionary stage.
Their evolutionary state is thought to correspond to
post-red supergiants rapidly evolving in blueward loops in the H-R diagram. In their post-RSG blueward evolution these stars enter a temperature range (6000-9000 K), called → yellow void, with increased dynamical instability. Their link to other advanced evolutionary phases of massive stars such as → Luminous Blue Variables and → Wolf-Rayet stars is still an open issue in stellar evolution theory. The most famous yellow hypergiant is → Rho Cassiopeiae.

See also: → yellow; → hypergiant.