(Astronomy)
Luminous Blue Variables (LBVs)
are a class of very massive
and luminous stars. They
are known for sporadically
ejecting a lot of matter,
likely due to instabilities
in their outer layers
caused by strong radiation
pressure from the core,
and are often found in
the conjunction with
planetary nebulae.
They are generally
found near the upper
luminosity limit of the
Hertzsprung-Russell diagram,
and most are believed to
have evolved from stars
with initial masses
exceeding 40 times the
mass of our Sun.
LBVs exhibit different
types of variations
occuring on a wide range
of timescales. The largest
variantions are associated
with sudden increase in
brightness by more than
3 magnitudes, lasting
for several hundreds,
maybe even several thousand
years. The smallest known
variations, sometimes less
than 0.5 mag, last from
several months, and up
to several years.
Examples of LBVs are
Eta Carinae, AG Carinae,
P Cygni and S Doradus.